This is for the gearbox guru's

I have picked up a couple of BA (I think) T5's aka M57. They both have fine spine input shafts

I want to know about part interchange, in particular

Can I swap in an earlier 10 spline T5 input shaft? Obviously tooth count and pocket bearing design will need to be the same. But otherwise are they interchangeable?

Anyone know input shaft tooth count options for the various ratio gear sets that were used

Anyone know input shaft length for I6 v's V8 versions?

Can I swap the gear sets into an earlier T5 mainshaft & extension housing like E-series? Again, mainshaft pocket bearing design would have to be consistent with input shaft. But would the gears physically fit the earlier mainshaft?

Thanks in advance