1970 Duster project in Sweden

Today I'm gonna try and get some time to continue to try and get that WOT stumble I have described in this thread Street Demon 625 experience so far

I have also been thinking of getting new gears for the differential. Today I have a 8 3/4 - 741 house with 3.55 and a sure grip. For the 741, 3.73 seems to be lowest there is out there. Is that correct?