The 85 motor is a somewhat different animal, it is the first year for water cooling, and kind of a lone duck. 86 on had powervalves, cylinders are interchangeable from 86-88 then from 89 on. The clutch was a weak issue, they had a coarser spline and only 5 springs. I use the newer bottom ends and have some motors with the 86-88 cylinder and head, the problem with this combo, you can't buy the power valve parts, they have been obsoleted, there may be other parts as well.
The motor made alot of horsepower for the chassis.