the guy i bought my fifty from put a later model 250 in it. he bolted the orginal 4 speed tranny right up to it and to this day i still dont have/need a crossmember for my tranny.
he fabricated the motor mounts himself, let me know if you want a pic of how they look.
i honestly would never do this change, its too complicated and alot of modification. just throw in a 235 or 261.
