Hi guys,
I sent a note to Perogie. They rebuild a lot of these Toploaders. From Steve's memory too, the only difference is in the detent system, springs (7234) and pins (7C316 and 7235). Ford was trying to improve the shifting with the HEH-BT but latter dropped. It must not have worked as well as they thought. I could not find any differences in the MPC, suggesting maybe Ford only serviced the HEH-BX detents. This is the answer I got back:
"The HEH-BT and BX interchange perfectly, both close ratio small spline, 28 spline, wide case units, but the earlier BT had the first revision detent system and Ford theoretically "Improved" the system changing the detents slightly They also changed the case as most BT's I have seen are on the mid-case lettered C5AR case (C5 casting number is in the center of the side of the case) and the BX's are usually on the more conventional High letter location for the lettering. Ford always changed the number in case of a recall or issue, but overall they were identical - and when I say the detent system changed, it was merely just a change in the spring and detent pin sizes, This is going off my head but if I think of any other changes on em when I see the bigger kahuna (who even with my 30 years around here, still knows alot more than me) if he knows any other differences."
Thanks all
Cory