1977 440 out of a van.
Saying the word "motorhome" is not very helpful. It's HEAVY truck / motorhome that generates the different heads and water pump. Like big Winnebagos, "class A" and not the "van nose" 3/4--1T stuff, the class C and B
On the "van" stuff there is probably little difference, other than intake, pan, and cam, and motor mount brackets
Here this might help. There's photos of the "high mount" water pump further down the page
http://www.forabodiesonly.com/mopar/showthread.php?t=246280
"Heavy truck" with high mount water pump. This setup has "wet" heat crossover. That is the what would have been exhaust ports in the head / intake are COOLANT
Even so if you can get these cheap enough, you can at least use parts of the short block, maybe even the rods.