Welcome to CHR!

Your block is a very common casting. Used in cars and trucks from 1972-78 it was the base for 215, 235, 240, 270 and 275 horsepower engines. The fact that it’s a 2 bolt should not disappoint as a 2 bolt block and cast crank can easily live with 450 horsepower.

I have seen a wide variety of casting identifiers in big blocks, i.e., "HI PERF", "HI PER P", "TRUCK", "PASS", "MARINE", and "TRUCK". As you have attested, it may be different front and rear. HI PERF or HI PER was used on most big block blocks and is not an indication of four bolt main caps or that it was destined for a high performance application.

Look at the front of the block, in the timing gear location. If you have a 010 stamp the block contains an additional 1% tin - 020 stamp means additional 2% nickel. They’re fairly rare and unless you’re a real serious racer, you’ll never get to the point in your build that it matters.

All stock big blocks use a 6.135” rod. As such, if you build with the 396 crank, you’ll want to use 427 pistons – I’d look to get a 4.00 crankshaft and make a true 454.

Hopefully Pat McCarthy will chime in as he is the big block master guru of the world (seriously, he is the best!)

Again, Welcome,
Glenn