First - core measurments are 15" tall by 18" wide, 23" outside to outside of tanks (max width). AFter looking at Ecklers and else ware it would seem my core is about .75" short top to bottom and too narrow on the outside max dimension.
72 4 spd, no AC.
Now, here is what I'm seeing. Tell me what you see.

1) I found the top rad baffle in my spare parts and installed. The rad core is too short and leaves about a 1.5" gap between it and the baffles bottom turned edge. 
2) The tank on the left should be to the left of the baffle (rad not wide enough), not hitting it, allowing the baffle to seal the top of the core.
3) Should the tanks be sitting on top of those thicker vertical foam seals? Would seem so vs. pushed up next to it like mine.
4) You can't see this, the top of rad, at the rear edge of the core, should be under the flipped edge of the shroud. There is a 1" thick foam seal to seal this up. With it installed, there is a .75" gap still. I would need 2 stacked seals to fill the gap.
5) The right tank is under the shrouds edge. The shroud should not be on the tank but on the core. It pushes the shroud away from the rad....leaving a gap. The right tank is kinda hitting the corner of its vertical foam seal. Not next to it or on top of it.
Conclusion: to me, it appears my rad should be about 3.5" wider and 1" taller to fit with these OEM cooling pieces. The rad is a copper replacement installed by the PO. It is pin mounted on the bottom with the little tower top center.

Whoa...  That is completely NOT the stock radiator for your car.  Look at the inlet.  See how it comes straight out?  Corvette inlets came out, turned almost 90 degrees toward the center of the car, and actually tilted upwards towards the hood. 

Also, look at the two bolt holes (at an angle to each other) on the edge of your shroud.  Those are for the brackets (missing on your car) that hold the radiator in place.  The one in your car is way too small. 

Very bad picture of mine below.  (Ignore the shroud and fan, it's obviously not stock.)  I have a '74, but am familiar with earlier cars and the radiators are almost identical.  See how much bigger it is?  And how it's held in at the top by the brackets on the outside of the core support. 

May want to get Joel to confirm, but I'm pretty sure that is not a Corvette radiator in your car.









|UPDATED|5/19/2014 6:39:43 PM (AZT)|/UPDATED|

Well....I say it does NOT appear to be the correct raditater for your '72.  It should definitely be wider, and the seals should fit between the rad and the core support. Iirc, the earlier cars did NOT have the two separate brackets to hold the rad in...just one in the center....I may be wrong.
Something is absolutely NOT correct there....

Oddly, I do have the single center tower on the top center. It just rides inside a bracket....kinda more like a safety stop because it does not really touch each other. Anyway, that one thing does seem correct for the smallest radiator, which my car would have had since its a 4 spd no AC car. And my rad does have its bolt holes for pin mounting in the correct place. I think it may be just a low end replacement rad. It does have a sticker on the side that says something like "AC Made" or similar.
Just to verify, you feel confident that the rad tanks should be on top of those foam vertical seals right? With a like 4" more width that would happen as would the shroud laying up against the core on the right side. I think the straight out top outlet is correct though for the smallest OE rad. Unfortunately no one seems to post the dimensions of these particular rads.... See here:

I looked again. If the drawings I found are correct, the aluminum radiator came with the center mount and the copper radiator came with the edge mount. Maybe the copper was for automatic or A/C cars? Both drawings showed the inlet being a 90 degree curve. Some replacements appear to have the straight shot inlets. Dunno...

Regardless, something's not right. You felt the top and bottom hoses? Both hot as hell when the car is at temperature? At least you'll know you're getting some flow through the radiator that way.

From your pictures, my gut tells me that the radiator is way too small. Both drawings I've found show, like Joel said, that the radiator goes all the way to the edge of the mounts and that the foam goes between the water boxes and the mounting.

The other obvious issue is air flow. I know you said the fan clutch is new, but that doesn't mean it's working. :-)

Before you invest in a new radiator, I'd suggest having the entire cooling system professionally flushed to see if you can clean it up some.

|UPDATED|5/20/2014 6:52:16 AM (AZT)|/UPDATED|

The straight outlet on the top I believe is for the later C3's. I know my friends '80 and my '81 originally had the straight outlet. I put a aluminum Be-Cool radiator in my friends '80. That came with the 90 degree elbow so I had to use a early C3 radiator hose as per Be-Cool's instructions. Awhile back I had my local radiator shop change my original straight fitting to a 90 degree elbow for my LS1 swap for easier installation. 

According to my Rik's Corvette parts catalog, you should have an 18" wide core aluminum radiator.  That is for a manual, no a/c base 350 '72.  The automatic tranny or a/c cars had a 26" wide brass and copper core radiator.  Big blocks had a 27.5" core.  So you may have the right size radiator and it just needs to be rebuilt or replaced.

Hey Gary, does it list the height of the rad in your catalog? The one in my car is short for sure at 15". None of the top sealing parts come close to to the top of the core. It appears to be like an inch short. If you look at my left side pic you can see how big the gap is under the baffle bolted to the core support. Also, I've noticed that the aluminum OE rads have minimal tanks on the ends...they do not protrude like the brass ones. That would make sens with the vertical foam end seals. Does your catalog show straight or curved top inlet pipe?
As far as flushing, the PO had been restoring this car for many years. When I bought it the engine had been rebuilt and recently installed with all these new parts including the rad, clutch fan etc. He told me when he was sorting out the over heating they had replaced the old clutch fan and installed the new Delco unit at a shop which had tested it. They said it improved the running temp. I dunno...but from the clutch fans I've replaced, they typically spin very free when cool if they are bad, or leak oil or make a ton of noise. This seems proper. Plus I've added the electric fan to the front. I think part of its overheating issue is a lack of proper sealing to the core support and shroud, but since it appears too small you cannot get it to seal using the stock sheet metal parts and foam.

Here's an old thread from corvette forum with some good info.

http://forums.corvetteforum.com/c3-tech-performance/1711100-72-factory-radiator.html

and here is a possible candidate off ebay:

http://www.ebay.com/itm/NEW-ALL-ALUMINUM-RADIATOR-1963-1972-CHEVY-CORVETTE-3-ROW-1-CUSTOMER-SERVICE-/281329130804?fits=Year%3A1972|Model%3ACorvette

Thanks Gary, great info!