Airhead engine, trans, final drive swap question
I've got a 1974 r75 frame with a 1976 r90/6 engine and trans mounted. I've got a deal on a one owner 1977 r100s. Seems the bike has been sitting, does not presetly run and shows 40k actual miles ( all records with the bike). Question: would the r100 engine fit my frame? Would the trans fit my r90/6 engine? Would the final drive be of any use to me, either mount with the r100 installed given it can, or be used with the present r90? I looked on max BMW and the only numbers that swap out for sure it seems is the trans. I'd buy the bike as spares for my r90 cafe, with the idea of rebuilding the 100s and installing it in the r75/6 frame at some point.. Any info would be appreciated. If none of the above swaps is possible I'd pass ( as I don't need another project). Asking price is $750.00. Seems just for parts the bike is work that.
1965 Cushman super silver eagle, 1968 BMW R-60/2, 1974 R-90/6 cafe, 2008 R-1200 GSA.