Anything 81 to 95 will 'work' ... and are interchangable. There are some subtle differences (like the kick starter) ... but they all work.
All of the 70 - 80 transmissions are interchangable too ... even those 4 speed (with kick) trannys on a 77 RS. Kind of fun ... but have you ever tried kicking over a 1000cc high compression engine?
It hurts, and God help your knee.
Fred * '85 R80RT G/Sified
* '73 R75/5 LWB
"Simple" with a Goal of "Ludite"