Since I am not up on the lingo, I will assume a CE block is a warranty replacement block for a 302. If you actually had the one that was installed under warranty and the warranty paperwork it would be about as close to numbers matching as possible. If its not the one installed and documented, a little lower on the scale but still better than a stick in the eye. If you haven't already, I would get the original owner to write as much of that kind of stuff down and have it noterized, not the best documentation but something. As far as the other numbered block, I would only use it if I couldn't afford the CE block since the car does still exist. If the guy that owns it has a change of heart, or sells it at a later date and then the new owner wets his pants to find out the original block still exist, you will have to disassemble your car to sell it too then. For the life of me I cant figure out why the owner of the other car wouldn't be interested.