Thread: Yz80 to 125 swap?

I just picked up an old 87 yz80 w/ no top end or carb for $50 and was thinking of swapping a 125 motor in it. Someone kind of local has an air cooled 125 motor out of a 1980 yz125 in running condition for $100 obo. I would obviously need to fab up some new motor mounts and pipe brackets, but i need some more insight on the project. It could be cheaper than buying a whole top end and carb.
I would like an aircooled so i dont have to deal with swapping radiators and the possibility of corrosion in older motors.
Whats a good way to set up the chain line?
Any other things i need to take into consideration about the swap?

drop a yz85 motor in it or find a cheap parts bike(s) and build one complete bike