I blew my 4.0 in my 1991 wrangler. Driving wise (I don't drive it anymore just when it started) it performed fine but just had a loud knocking sound. I assume I am bending one of my pushrods or something along those lines. I was either going to rebuild it or look for another one to swap. What is the compatibility with the 1991 4.0 and the 5 speed manual transmission? What years 4.0's will drop right in? Also what transmissions can I do this with? My '91 does not have the external slave cylinder, and newer ones do which is what I would look for. What years will bolt right up to the 4.0's that fit my 91? Thanks.