Dogface,
If you want to know about change to ring & pinion gears in a 47-54 3100 torque-tube rear-end, the only conversion that is available is a 3.55 R&P set.
I have that conversion in my Suburban, with an SM420 4-speed. First gear is still too low, except when I need it with a full load (a full set of 7 passengers).
The big advantage of this setup is the the ~15% decrease in RPM in high gear. Also, if you install the bearing/bushing installation kit, you will most likely experience a much quieter cab.
