Bruce,
Actually it depends upon the
B7100's age.
As mentioned in one of the other posts, there was a gear drive
B7100 model produced from the mid-70s to around 1984. Additionally, at least the way the story is told to me, the
B7100 production stopped for one year and then resumed around 1985 through 1998 with the hydrostatic transmission (there may have been a period during the 1985-1998 production run where both gear drive and hydrostatic transmissions were available).
Obviously there were many more B7100s produced compared to the
B7200 since the
B7100 was in production for a much longer period than the
B7200, but parts should be readily available for both.
For 4WD B7100s, the older models had a 4-lug front wheel and no ROPS; the newer models had 6 lug front-wheels and ROPS became standard equipment around the late 1980s. I THINK that the 2wd tractors all had small 4-lug front wheels.
I can't validate the year range given for the
B7200 but it sounds reasonable.
B7200 Advantages: The
B7200 might possibly have position control where the
B7100 does not. Also, I believe that the
B7200 might have a tachometer where the
B7100 does not.
Other Advice: Be sure and become educated on the "thermosiphon cooling system" the
B7100 uses (the
B7200 probably uses the same system). With no water pump nor thermostat, it is a good system but different and you can ruin a good engine if you don't know how to perform routine maintenance (example: putting more than a 50/50 mix of antifreeze is very bad...).
Good luck and hope this information helps,
Kelvin