Motorcycle Repair: 1977 Harley-Davidson Sportster Engine/Transmission Swap, harley davidson sportster, evo motor

Question
I have a 1977 Sporster with a Wide Glide front end, fat bob tanks, softail rear fender, but the original drivetrain/frame of the Sportster.  The engine runs like a champ, but the transmission and clutch have given me problems for years.  Last night the transmission got locked in third gear, but had been grinding and clunking for about two weeks.  I think it is a major problem.  I would rather spend the money on a new/used engine and transmission combo, than rebuild the current transmission as my cases are tired, beyond tired.  The bike leaks more than the typical AMF.  My question, is it possible to take the engine and transmission out of a newer Sportster and bolt into the 1977.  I have seen a few 1993-2005 Sportster engine/tranny combos for sale, and would like to buy one and put it in my old Sportster.  Can it be done, and how hard is it?  I m sure I would have to install a belt drive system as well, but do the mounts line up?  Would I have to have new welded in?  How about the wiring?  Thanks in advance.

Answer
I think you are going to run into problem trying to put a EVO motor in a Shovel frame. The motor mounts are going to be different and you would have to do alot of fabrication to make it work. Also, the 77 clutches will not work.
I can rebuild your motor and repair the trans cheaper that what you want to do.
Good luck and happy riding
Mike