Of course the 4.1 low would be nice, but I dont fully understand what is used. I just scored a SM465/205 32 spline from an 86 1 ton chev with all the hydro parts and only 28,000 miles on the clock. I want the hydro and need the SM475 because I blew the rev gear in my 76 SM465. Problem is that the coupler on the hydro SM465/NP205 is gone and GM no longer has any. I have allways wanted a doubler and if I under stand the set up the gen II replaces the coupler. If it dose I am just one more step closer to a doubler. So is this the case, and either way what do I need and how much $$ to hook me up? My 203 is a 27 spline chev that I know nothing about it's origin.