Hi there chief,
I think you will struggle to get any internal gear parts from a B7100 into a B7001 back end, maybe the odd part here and there.
they may be very similar in respect to casings etc, and body work, even the same engine but, there are a lot of different parts internally and externally.
and that includes inside the rear end.
The b7100 and b7001 are not the same machine, and as far as transmission etc goes, the 7001 is closer to a B7000.
I have been downthis route and had both rear end open side by side , the differences are all over the place, even the pto shafts and gears are diffenent.
but, the pto output shaft oil seal is the same item on both 7100 and 7001, as i have ordered the same part for both of my machines, as are the axle shaft oil seals etc.
sorry to put the dampers on it, but you need to be very carefull when swapping rear end parts between 7001/7100 etc, same applies to 6001/6100 etc.
they look the same machines but they are not, but there is nothing lost in trying and you may just find some parts that you can retro fit.
thanks
rob