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?
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The 452 heads with the steam ports were police application, the heads had steam ports on each side of the spark plug and took a smaller taper seat plug ,
These heads work fine on a reg block and if you drilled the steam holes in the block deck you get the extra cooling , most late gaskets had the steam holes
The true motor home big blocks were the 413 with the massive water pump and housing and the strange
big block heads that had the plugs up top like a small block with different exhaust ports
