OK I understand wanting correct numbers. For you non chebbie guys ... GM stamps VIN # the block in addition to date codes etc... If the build was not a numbers matching deal then go for the extra cube's. Not to mention there is no visual difference between a 302 to a 350 CI engine block. It is sad but you can't do a complete rebuild on that 327 for the price of the crate engine, and a 100K warranty.
I would store the #'s correct block and install a factory built engine with all the new technology but correct visuals. I think the GM759 (350 CI) has a fuel pump boss - 4 bolt mains - roller cam and alum. heads. You can install iron heads for the right look but ???
The classic intake with
oil fill tube will bolt on to the alum. heads too. The other consideration with new alum heads would be center bolt or perimeter bolts but they now market a plate to adapt for older valve cover mounting. The 759 does have a cast crank but also has the composite conn-rods that are very cool. No hyd. cam to roll dice on!
The 327 was a great engine and loved and lived at higher RPM. If I was willing to pay for a complete rebuild anyway I would build a 377 in a heartbeat!!! Overbore the 327 block, install an offset ground forged crank (now available aftermarket). Use GM pink rods or aftermarket replacements and a small base circle cam with thrust plate and rollers. I ran this exact build for many happy years. When tires and suspension got better the big blocks started kicking my arse on a regular basis so I went big block.