The ratios on a Spicer/Brown-Lipe 6231A are: 1.24 low, 1.00 direct and 0.87 overdrive. I believe the 5831A is similar. The A suffex is important. The B and C are not progrssive and give like a 2:1 low or other less useful variation.
With a small engine you can work a big load up through the gears by keeping the engine on-the-boil. The RPM drop between gears is around 400 RPM. A 13% overdrive is not such a big deal to pull as a 30%. Aside from the ratio problems, a Clark 5-speed is difficult to get parts for these days I'm told at the ATHS antique truck show a few years back. Someone there suggested that I convert to a 10-speed roadranger but I've already got 12 speeds, 9 road gears and 3 compound ratios.
