I am looking to buy a 1970 vette with a an L-46 350 engine

I think the temperature was normal, but the car is several hours away, and I am going back tomorrow to see it again and finally make up my mind. I did not drive it on the highway the time before, so I plan to do that this time and look for overheating problems, pulling or abnormal vibrations. I will also put it on the lift and check for leaks and ive read on here to move the back wheels to check for worn bearings. I just remembered I noticed the oil pressure was pointing low at idle. It is all original and has about 90K miles on it

A '70 model has a mechanical/hydraulic oil pressure gauge, so if the reading is low, chances are the actual pressure is also...
One rule of thumb is 10 psi oil pressure for every 1000 rpms is sufficient. Look for the pressure to drop when you get on the throttle hard. If it does, that's a good indication of worn bearings, with too much clearance.
Does it make any noises at idle?
Just having a low reading at idle could simply mean it needs an oil change, or the oil pump might be failing. I would suggest installing a temporary gauge that would give a number readout, instead of a "Low-High" reading, if possible.
I would definitely point this out to the seller, and use it as a bargaining chip.

Good luck on the test drive...hope it works out!

How easy is it to stab in one of those temporary pressure gauges that you are talking about? Can I get one at the parts store?

You can get one at most parts places. It's fairly easy to install temporarily. Just dis-connect the oil pressure line at the oil filter area, and connect the line from the temporary gauge. Should be able to do this in just a few minutes from underneath, a little longer from the top. Just go ahead and assemble the line on the new gauge before you get there, and that way it'll all be ready to just swap the lines on the fitting...usually takes a 7/16" wrench, but it could be smaller(3/8"), or larger(1/2").Then drive it until it gets warmed up, and see if the test. gauge reads the same as the vehicle gauge did.
Hope this helps.

And be careful of the way you route the new gauge line...make sure it doesn't get around the exhaust, or anything else that may damage it. Adams' Apple2008-10-16 21:35:18

Thanks for the info

It could be a bad gauge, but it is not too likely.  I have had experience with bad mechanical oil pressure gauges.  They usually work or don't.  If you put in a temporary, just tape it under the hood somewhere and go look at it.  Be especially careful not to get the plastic line close to the exhaust or you will melt it and lose all your oil.

If pressure is low at idle, even if it still acceptable, it means the engine is getting well worn.  If it has good compression and doesn't smoke, you might be able to replace bearings and oil pump, and be all set.  Those can be done without removing the engine from the car.  Materials would be less than $200.00 if you can do it yourself. 

Larry