Welcome Ed. I got your E-mail on this tranny. The one in my truck was retro fitted, not factory. I beleive what you have is the SM318 w/the borg-Warner overdrive. This trans is a direct bolt in. I'd suggest that you use a premade wire harness to save the wireing headaches. The harness is being reproduced for the v8 models, but it will work fine with the 6. I also added a separate switch to shut the power off to it when not in use to save stress/wear on the electricals. I really can't give a feul milege for mine, as the engine isn't stock and my milege isn't real good to begin with. I can tell you that the o/d is a real joy on the open roads. I cruise at 75mph easily only turning about 1900 rpm. That's with a 30" tire and 3.90 rear gears. Some of the parts are hard to come by, but most of the primary trans parts are the same as the standard 3 speed. here is a link to the '55 manual showing how it hooks up.
http://chevy.tocmp.com/1955truck2shop/55ctsm0715.htm
