Well my count is up to three 600+ hp 360s.
Blazin' Bob, any new casting gets a new casting number. Even if it is a little tiny change. Or maybe the mold cores are starting to flake.
The only time a significant casting change was made without a casting number change was the last half of the run of 451 heads for bigblocks. Engineering corrected some thin areas to make them safer to port but because the bigblocks were already planned to be out of production they didn't dare give it a new casting number. So they instead put the number "1" on the end of the head.
Casting numbers increase with time as more and more castings are designed. So for example a casting number with a 1 in front is probably from the '50s, 2 would be '60s, 3 would be late '60s, etc. I think the casting numbers are in the 5s nowadays.
In the early '80s you could buy a bare 452 casting for something like $59.00.
R.
I'm not going to say that there aren't 600 HP stock 360 blocks out there running but how about posting up your average ET's at the track, weight, and track and corrected altitude. Let us do some number crunching.
