440-3 is a 3rd casting.
There a two versions of the 1976-78 452 heads. Standard and the 452 motor home head with the steam ports at the exhaust valves. All the later blocks have larger cooling ports. I've had 1976-78 blocks from cars, trucks and motor homes and were all the same.
That is the first I have heard of 2 versions of the 452s.
I had always thought that the heaviest duty commercial chassis 440s had heads with more water passages around the exhaust and spark plugs meaning that they were different castings. Otherwise all other 440s shared the same 452 heads. But you say that they were all the same heads even on the heaviest models, just that they had more holes drilled?
I do wish that we could still get the commercial chassis thermostats with the block-off plate on the bottom. It takes some experimenting to get the by-pass hole in the water pump just right. The thermostat with the block-off was a better approach to that.
