Well heres the scoop on what i know. a buddy of mine has an 86 fa 50..im pretty sure its the same...he is the one with a puch head on his. i know because i put it there. what we had to do was file out the stud holes because they were in a slightly diff location. it is quite the power remedy. good for about 35 on stock everything else.
as for the exhaust. also we used a puch exaust. why the puch parts you ask? because i have an abundence of them. we cut down a puch exhaust pipe and welded it to the shuttle header. its now good for a steady 40 mph flat land. i can arrange for pictures of the mods if you like?