Without taking transmission apart and counting teeth, it appears 4th is about 0.5:1, 3rd about 1:1, 2nd about 1.36:1, and first about 1.9:1.
Thomson would have had 6.6:1 final drive nominally with 12-36 (60 inch dia) or maybe 13-36 rears while regular WC would have had 4.7:1 final with 11-28 rears (50 inch dia)
Regular 1st was 2.5 mph and 4th 9.5 mph. So Thompson with single trans would have been about 2.1 mph in 1st and 4th would have been between 8.1 mph with 12-36 and 8.5 mph with 13-36.
So 1st 1st would have about 1.1 mph and 4th 4th up to about 16-17 mph.