My project car is setting in Las Vegas right now and I'm trying to see if the numbers match.
The Vin is 342571z105116. I ask the shop guy to get me the engine number and he text me back 396021F which don't match anything.

The car is suppose to be a 1971 Cutlass SX-455.

Are we doing something wrong?

Thanks for your help.

 

The number you want is on a machined pad on the block under the #1 spark plug hole.

 

And assuming your SX has A/C it's partly blocked by the alternator bracket.

 

OK, thanks what is the number he sent me? Would that be off the head?

 

That is the casting # for all 455s located above the water pump (396021)

 

The block casting #

https://classicoldsmobile.com/forums...what-year.html

 

Just so we're all clear, the numbers that "match" are the VIN derivative stamps on the block and transmission. The VIN derivative is a partial VIN that is nine characters (the VIN is thirteen characters). The first character of the VIN derivative will match the first character of the VIN, and the last eight characters of the VIN derivative will match the last eight of the VIN. In your case, a numbers matching block and trans case will have the VIN derivative of 31z105116.