koolkar, if the engine is 87 and up, just look the casting number behind the driver's side cilinder head, there will be a 5.0(305) or 5.7(350), if it is a pre 86 engine, You'll have to check the casting number to see what You've got.
Also, if the heads are off, the bore is 4", the 305 is 3.730, both std size.
As for the damper, except the 400, all other small blcks are internal balance, so a damper from one will fit all other, except the 400. So depending on the engine year and model, you can have almost any damper in it. There were a big, 8" model that was pretty common on 305, but not a general rule. I've found both the 305 and the 350 with some weel assorted damper sizes.
