Well, I found a nice block here in NJ on craigslist. It's allegedly out of 1971 GTO convertible that some guy swapped an LS engine into. He traded the 455 engine for the LS engine but left the 455 at the machine shop for six years so not much of the engine was left at the shop as you would expect if you abandoned your engine somewhere for 6 years - just the block and some misc pieces remained.
The block was bored .030 over. The current bore is 4.180. Looks like it may have been bored and then used as a door stop at the machine shop for half a decade.
It's a 1971 YC (455/325 horse D-port) engine with two-bolt main caps. Maybe...
It's got a casting date of F050 (June 5, 1970) with a "70" cast on the back of the 9799140 block. Is it a late 1970 cast block from an early 71 455/325 horse car? or it is a late 1970 455/360 horse engine that was the one year only 455HO high compression engine? Feel free to chime in with more info if you have it. It seems to be a weird code/year from what I see on various websites and I don't seem to be the first person to run into this conundrum.
The partial VIN looks like 221302638
I spent the afternoon chasing every bolt hole and then scrubbing the thing down and finally power washing the cobwebs out. I then used a scotch bright on the cylinders and oiled them down once everything dried out.