Ok, with all the stickies here, here may be an idea. I've had several call about my 103" engine from my 2012 streetglide, most of the first questions is " will it fit in my bike"? The latest is a 1990 electraglide.
I know the 5spd and 6spd trannies have different bolt patterns. So my answer was "no". But that could be changed as well. So what years and models all interchange?

 

a twin cam will fit in a '99 and up frame.

to fit in an evo frame, modifications are required, more to the tranny mount area as the twin cam tranny bolts to the motor, earlier big twin trannys mount to the frame, the bottom of the frame would also need modding to to fit the oil pan

the twin cam motor is not as "tall" as the evo, so the back bone likely would not need to be modified.

this is merely informational, you don't want to get involved in a "what fits what" with a buyer who is obviously a novice

once mounted the motor would still need fuel and spark controls


Mike