Is the "motorhome" like a big Winnebago motorhome or is it "van-based" with the front end looking like a B-series van? 1978 was the last model year for the 440. On the later model years, there should be a pad just above the oil pan rail (rh side?) that has the VIN stamped into it, I believe. That should nail it, but if it was in a big motorhome chassis, with Chrysler only supplying the rolling chassis, it might not. Don't recall any 400s being in motorhomes!
As I recall, Chrysler/Dodge's last attempt at medium-duty trucks was in about 1972. Motorhomes lasted longer than that, model year wise.
There was a unique motorhome-only 440. One distinguishing external feature was that the exhaust ports were all separate, like a big block Chevy. The combustion chambers looked like A-blocks. Took an A-block style spark plug. Intake ports were normal B/RB Chrysler. Great exhaust ports! Had a specific 4160 Holley that went on it. I saw one of these heads a while back at a machine shop. Looked unusual and interesting!
CBODY67
