I would stay away from the slimjim as I have heard they are not that good of trans,a 59 or 60 jetaway would be the way to go and should bolt to your motor if you get the flywheel with it. I know where a few 59 and 60s are in some junkyards around here,as for rebalancing the flywheel you would have to talk to someone that balances motors or look in hemmings. Tanson enterprises is one of the companies to modify a moder GM trans to the 49-64 olds motors,their number is 916-448-2950. I know using something different is not easy as I have a 37 chevy p/u and would like to keep the 235 6 cly but if I cant get a modern manual o/d trans to work with the motor I am going to put in a V8 in it. If you are interested in a 59 or 60 trans and are close to dayton ohio I will take you to the yards that have them. Jeff