I found a XR600 swap to a 360 on ChopCult. Here are the owner's comments:
The only mount that "lined up" was the top CB360 mount which had to be drilled out to 8mm and slightly offset to get the correct chain line.
The engine has plenty of room in the frame. It's narrower, shorter, much lighter and roughly the same height.
Mods needed were-
fabricated inlet manifold
fabricated exhaust system
fabricated oil tank
fabricated foot pegs and mounts
cut and reposition bottom frame bar
I used the xr alloy engine mounts and made new tabs on the frame for them to attach to.
new oil lines
14t cb360 front sprocket(fits xr engine)
modified gear lever
modified brake pedal
modified throttle cable
slight massage to the underside of the tank
the wiring was really easy and it eliminates the battery.
I really wasn't too difficult, just one job at a time and before you know it your done. I could have modified alot of the XR components to fit, but I enjoy hand making as much as possible.