I know the car is an original 350, but where on the block is the vin stamped or info that will tell me if it is indeed a 350?

I don't think you can see the casting number without taking half the engine apart. Its on the back right hand side. See if you can get he casing number from one of the heads, that is a lot easier to get to.

the casting number for the heads will be underneath the valve covers, stamped into the iron.