3.6 x 2 = 7.20
3.75 x 2 = 7.50
The rear ratio that fits is the Chevrolet 15,000 pound, 7.20 ratio.
If you can find a 6.50/8.85 vacuum shift 2-speed you will gain about 10% or 5-6 mph. This pumpkin should be a direct swap other than the drive shaft may be to long.
Or you can look for a 6.17 single speed and swap pumpkins and gain about 15% or 7-8 mph, but you will loose pulling power when loaded.
As a side note, how often will you be loaded, are you putting this truck back to work?
Mike B
