Took the engine out of my 1992 Z-28 that I purchased last year. Tore it down last weekend and looking to start the rebuild. It's a 4-bolt main with a one piece rear seal with roller lifters. I didn't think the L98's came with a 4-bolt main, so I started looking at the block numbers. The casting number is 14093638 - 350, 2 of 4 bolt, 87-95, roller or flat, 1 piece seal. I can't make out all of the engine number, but the last 5 digits are 126PHH. Could not find the PHH suffix anywhere. There is no VIN number stamped on the pad either. Does the PHH prefix mean it's a Pontiac? Is it a replacement crate or truck motor? I wanted to keep this a numbers matching car. Is that important? Thanks.

 

it sounds like a replacement motor. 638 block was available as a 2 or 4 bolt main and roller or non depending on application.

 

Absolutely not, unless it is a "rare" model. ie: one of less than 1000 produced. (doesn't include such as "only 5 produced in puke green without T-tops but with TPI 350")
The engine may be a factory replacement short block, long block, or a transplant. It doesn't matter because it sounds as good or better of a block than came in the car.
The only differences would be pistons, cam and heads.
Check the heads. Everything else will be changed on rebuild anyway...