[Slick61]

I've got an aluminum 427W with a fairly snotty cam... aluminum flywheel too. I'm running a 3.73 rear end & the TKO-600 with the 0.82 overdrive. When I first got it, I thought I wanted the 0.64 as well- but as I drove it more, I discovered it was set up perfectly. My engine doesn't come on-cam til about 2400 rpm, so the 0.82 is ideal- especially for freeway cruising. 2700-3000 rpm is an uncomfortable cruising range??? For my engine, it's the sweet spot... sounds amazing without being too loud. My engine could never handle cruising a 1900-2200 rpm... it would buck like crazy. As others have said... it's the combination of engine setup/cam profile and rear end that will dictate the best overdrive for you. Good luck with your build!