I just installed a Baumann transmission controller for my 4L60. I just drove it last night for the first time. There is still some "getting used to the program", but at this point, it seems to be a nice product. I would be carefull about the 3.73's, unless you have pretty big tires (say 28" or bigger) 3.40 would most likely be enough. My advice would be...Get the engine/transmission in there & drive it a bit, then decide on rear gears. Lorne