When the orginal t4 input shaft bearing gave up due to a previous owner not replacing the pilot bushing, I got a t5 from a guy who said was rebuilt with world class t5 specs. Well.. 11 months later,  
reverse broke, and second sounds like a rock polisher.
my 1980 cj7 has a modified 258c.i., dana 300 t case and runs 32" muds. I have been wanting to swap in a sm465 that I got out of a 3/4 ton GMC w/454ci. 2w.d., it works and was free, and has been in my yard for 2yrs. is this going to be a headache conversion that will never seem right, or is it worth the time & money?