D2 5J with a 5U trans and diff

I have a 1944 D2 5J with frozen steering clutches, no idlers, bad tracks and rollers. I picked up a 1951 D2 5U with good tracks, clutches, swing frames and rollers however it's missing the engine. It appears from examining both parts manuals the only difference is the flywheel at the engine/trans interface. The transmission housing casting numbers are different, the 5U is 8B9370 the 5J is 5B5692 and track with the parts books. All parts aft of the flywheel are the same including the pilot bearing. It appears from looking the trans/engine flanges are the same--will this engine mate with the newer transmission?

Yes they do.

You're going to loose quite a few hp and advanced engine technology.

Yes, but you will gain a running tractor with a snorty little engine.