I'm thinking if Datsun mainshaft gears have the same ID you may be able to mix and match gears so that in order to change ratios only the countershaft needs to be remachined. Basically I'm looking for a way to cut the costs, if you just have to mod the countershaft rather than both the countershaft and make a new main shaft gear. It's likely not possible but I'd love to know without taking my 60 series box apart.

I have picked a 4.625 ring and pinion with the intent being that mostly 3-5th will be used but there are two corners on my locks track that will require 2nd gear. As you know the gap between 2nd & 3rd is huge. I just had a 56 series close ratio countershaft repaired and that was reasonable ($600 U.S, if I can get the 60 series modded for,around the same amount it would be total worth it.

Tom