Stock gearing (42/14 internal ratio of 3) with stock pinion and spur
1st 48/16 x 3 = FDR 9
2nd 44/20 x 3 = FDR 6.6
upgraded gearing from igt8 (43/13 internal ratio of 3.3) with stock pinion and spur
1st 48/16 x 3.3 = FDR 9.9
2nd 44/20 x 3.3 = FDR 7.26
Stock gearing (42/14 internal ratio of 3) with pinion and spur change
1st 49/15 x 3 = 9.8
2nd 46/19 x 3 = 7.26
At least going with just the pinion and spur change you would have more gearing available for different tracks. Of course I'm not sure if the spur and pinion combo would mesh ok. That may also limit the gear use 1st 49/15 and 2nd 46/19.