I'd check the serial number on the frame, the engine could be out of anything... Frame serial number on my 40 is at the very front, passenger side, outside, just behind the bumper gusset.
Have you read the VIN off the frame? Could it be a 55? I am definitely no expert, but something seems odd...
I say that because;
1) the rear end does not look like what I would expect a 40 frame to look like. It has a crossmember at the back with a tire hanging chain, just like a 60. Not...
I do need parts, I need the back end of a frame, but that frame is totally completely different from the frame on my 40... In fact, the only resemblance I see is the tranny and steering!
Uuuuuummmmm. Hate to break it to you, but according to your pics in the drop box link, that's not a 40, it's a 60.... And more likely an '83-84 since the 60 wasn't built in '73-'74
Might get more interest if you change the title to reflect that, or is it the wrong drop box link?