What about checking the pad stamp on the front of the block before you even mess with the casting numbers? The stamp pad has the partial VIN and engine code, and it's usually a smoother surface so rust doesn't eat into it as bad. I carry a little squeeze bottle of CLR and a brass brush in my swap meet bag, and if the pad is still too far gone I just walk. No point dropping cash on a block you can't ID, and a seller who won't let you clean it up first is hiding something.

The returns eat the savings" got me too, I used to just buy pre-cut.

So you're telling me I've been leaving money on the table by actually fixing it right the first time?