there are 2 sets of BB #452 heads 1 set has extra cooling passages around the spark plug hole and use the 5/8 hex 'peanut" plugs. AKA-#452 motor home heads.

the other set does NOT have extra cooling ports around plug holes and use a 13/16 hex plug. AKA-#452 car heads.

look at the plug hole, the MH #452 head will have a small machine area around plug hole with a small bump in the casting below plug hole. extra cooling port under bump. hence small plug & machine area. (FYI a 13/16 plug will screw in and work as that is what I found in mine at the start, but not ideal fit looking at head on bench)

it also had head gaskets that blocked those ports on block/head so it worked this way either head from what I can tell.

the car #452 head has a larger machine area around the hole and no bump in the casting.

my 77 440 MH engine had the peanut plug heads and I swapped to a fresh set of car 452 heads 13/16 plugs.

I looked into all that when I swapped heads. no cooling issues with mine.

only time it ran hot was with retard timing. stays at 185* now it tuned.

only way to use those IND/MH heads is to use the raised WP housing and exhaust manifolds.

but you can take the IND/MH 413 short block bore & stroke to a 426 wedge as that is the ticket for using one of those IND/MH engines to get a cheap 426 wedge/max wedge clone.