You had this car appraised right? So they didn't take into account whether the drivetrain was original to the car or not? Hmmm.

The numbers for the carb run verticle on the main body casting just forward of where the left rear bolt goes down through the carb.

There are a few casting codes on the block. One is on a pad next to the distributor( date code). There is a block casting number on a slanted part of the block...passenger side behind the head and just in front of where the transmission mates up to the motor.

There is a two letter code on the pass side next to the water pump and below the head.

There's a date code on the heads as well on a flat area below the bottom edge of the valve cover and there should be two big casting numbers on the center exhaust ports of the heads.

All these areas are generally pretty dirty and caked with grunge so it takes some effort to get to them and clean them off good enough the read the numbers.

I think if you go to the Wallace Racing site they have a diagram showing where to find all the codes or just google Pontiac engine codes and something will probably come up that you can use.