The only 4 speed that's a bolt in swap has a "granny gear" 1st. gear that's useless for street driving. It's there to get a maximum load in the bed (or a big overload) moving on an uphill grade. Going to a newer design automobile 4 speed like a Muncie or a Saginaw will also involve changing the entire driveline- - - -driveshaft, rear axle, etc. Ditto for the 5 speed T-5 overdrive trans which is what all the cool kids do these days! A couple of years ago I was involved in swapping a column shift 3 speed to a SM-420 4 speed in an early 1950's 1/2 ton truck. Just finding all the parts to do the conversion took several months, and the universal joint at the back end of the transmission is almost nonexistent these days. Translation- - - -"E$$$$pensive!)
Jerry
