The 904 evolved into the 500 which was later renamed the 42RH. The 727->518->46RH. 1996+ went to the RE models which are useless to you so make sure you don't get one of those.
I have read others who went to the GM 4 speed autos for better/cheaper aftermarket support and a smaller physical size to not have to cut.
One day when I get off of my ass, I want to get one of those A41 4 speed kits from Silver Sport. They are based on the GM 700R4.
