As a hobby, I buy and sell stringrays. Depending where the car is, I could go with you.
Here is what you need to know.
Where do they rust?
Check the frame closely, especially on the rear kickups right before the rear tires and on the windshield frame. Bring a tape measure and measure the wheelbase on each side.
What should they cost assuming non SHOW quality. its a project
Stringrays have went up in prices, expect a 81 project one to be anywhere from $8 to 12K. Number matching engine and the VIN will be on the 12K side.
What motor should be in it.
For 81, there was only one engine option, the L-81 which was 190 horsepower.
What other things are known to fail.
Get the best looking complete car you can find, vette parts are not cheap.
On a side note, Like Miller said, I know where a 73 454 vette(matching numbers with 76000 miles) is for sell and it is a deal at $19500 located near Galena. No, it is not one mine.