Check for date codes on the head and block, they will be something like (B239) where the month is the first letter( A=January, B=February. etc..),the day of month are next two digits, and the last is the year '79 or '69. The year is a tough call, it could be two decades apart or even three.
The newer heads will have the intake cast right on the head, older engines have the intake as a separate piece. All the heads are about the same just as the blocks are.
Check the area right above the top water pump bolt by the first head bolt( drivers side). This is the weak spot of the block. If the head bolt is over torqued, it pulls the block out of shape and cracks it where the water pump bolts on. They still run OK only they leak coolant from the crack. Its not repairable so look close.
If you rebuild it, install a flat top 307 Chevrolet V8 piston, its a bolt in swap but will raise the compression up to around 9.1 to 1. You will still be able to run regular gasoline but the performance will be improved with out spending extra money.
Joe
Last edited by Joe H; 03/13/2009 4:37 PM.
