An excellent technical write up on the conversion of the 6 to 8 speed conversion of the 404 Transmission. The only caveat that we would suggest is to understand what you are getting in the end.
#1 - Your Low 1st Gear is Still the SAME.
#2 - Your High 4th Gear (8th Gear) is still the Same as your regular 6th Gear.
#3 - You are getting 2 additional gears in the middle ranges!