I have a customer with a 1969 tri power 427 vette. The hood has the 427 emblem on it. The problem is what 427 H.P. rated engine does he have? He thought there was only 2 but I know of at least 4. He thinks he has a 435 hp engine, but I told him those engines are aluminum head solid lifter cam, tri carburetor engines. His center console tag says 10.25 compression ratio, in My old Motor manual that says 4V 400 HP 427 cubi inch engine, so it don't jive.  I told him to find a cowl tag to identify the engines, interiors, etc. he can't find it. so my question is: where do you find an I.D. tag to tell you the 2 letter suffix of what h.p. or carb setup this car has. If its missing the tag, how do you find out? thanks.

Most 427 engines had cast iron heads...only rare L88 and L89 427's had aluminum heads.  

Without the build sheet, it's impossible to tell for sure what engine it had originally. There is nothing in the VIN to tell. Other tell-tale signs can be faked, such as the tach, fuel lines, etc.
Corvettes do not have a "cowl tag" like a Camaro, or other GM cars do. There is a "Trim Tag" that gives the body build date, and paint/interior color codes, but nothing about what engine/trans or other options the car had.
Check the casting # on the rear/top of the block, and the Stamp pad at the front of the block in front of the passenger side head. The stamped numbers/letters there will tell what engine the block is, and what configuration it was originally.
Adams' Apple2009-10-23 05:13:12

The block is correctly either a 439, or 052 casting, and they used both castings for all HP options, so that doesn't tell you anything.  The stamping, if it still exists, will, as Bruce and Joel said, will tell you what the original configuration was.  The 435 HP heads are 840, and the 390 and 400 HP iron heads are 063.  If aluminum, 435 HP used 842, and L88 used 074.  Only 435 and L88 used square port heads.

There are other signs, like the half-shaft flanges, red line, etc.  The console, tag while easy to change, does tell HP, torque, and compression ratio.  The 400 HP used oval port heads, tri-power, and had 10.25 compression, so that sounds like it matches what you know so far. 

And of course, it could all be faked, and it could be an original small block car.  Only the built sheet will prove anything.

Larry

  Larry, what are the 840, 063, 074 numbers  you are talking about? are these casting numbers on the heads? I think your right, this is a 400 hp tri car. He has owned it about 13 years, I will give him this site so he can register it. We will look it up over the weekend, I will let you know. I am suprised that they didn't keep better records on Corvettes, I thought they would have a cowl plate!

I am sorry.  Those are the last three digits of the casting number.  Chevrolet nuts use that shorthand without thinking.

Larry