Motorcycle Repair: Honda 650/750, honda 650, honda motors

Question
I hope I'm not too far outside you area of expertise. I have 2 Honda motors, '78 750 and '81 650 (I think those dates are right). The 650 is missing from the head up. I was wondering what parts are enterchangeable. Can I make one motor out of the two? Should I rebuild them seperately? Any advise you could give would be greatly appreciated. Thank you.

Answer
The only way to tell is to pgysically compare the parts.  Honda is well known for making very small but difficult changes to parts even for the same models when the year changed.  You can also check the part numbers, since if Honda used the same part, it will have the same number.  I would re-build the complete engine you have first and then look for parts to complete the other one.  Good luck,  Jan