The FMX was not a Ford transmission, Ford just bought them from Borg-Warner, as did many other manufacturers. It was introduced in 1968 as a redesign of the Borg-Warner FX/MX transmission that Ford had been offering since about 1951. It is a very strong transmission. Ford even used it behind milder big-block applications. The Borg Warner FX/MX was used pretty much across the board as far as models of cars go. Other names for it were Lincoln - Turbodrive, Ford -Cruise-o-matic / Ford-o-matic, Mercury Multimatic / Merc-o-matic, Nash & Rambler - Flashomatic, Studebaker & Packard - Flightomatic.
The FMX is a considerably strong transmission, redesigned to cope with the horsepower increases in the mid 60's. It does not have much aftermarket support, only torque convertors, HD clutch packs, and shift kits, so it's limited as to how much you can increase it's strength. This is so for several reason, but primarily because the FMX has a cast iron case that weighs a ton so it was never a choice for drag racing.
AMC used FMX trans in the Ramblers. Studebaker used them in the Hawks and Avantis with different valve bodies than everyone else.

pan gasket

Band Adjusments for Borg-Warner Automatic Transmissions
Adjustments
Front band setting--Back off adjusting screw and put a .250in spacer between the adjusting screw and piston pin and tighten the screw to 10 inch lbs. There should be a one-way clutch spring on the adjusting screw that will automatically adjust the front servo. Older units had a lock nut. [ Tighten lock nut to 20-25 ftlbs ]

Rear band setting---unlock jam nut and back off adjusting screw until free travel is obtained. Tighten adjusting screw to 10 inch lbs--then back off screw 1 and 1/4 turns. Lock jam nut.

[ Note: the front band adjustment is the same for most BWauto transmissions. The rear band adjusment is similar, with the number of turns the screw is backed off differing between the IHC, AMC, Ford and Studebaker Applications. Make sure to check the specification for the model that you have. The tools called for are simply preset torque wrenches. The torque setting of 10 inch pounds is the same for all models.]

--------------------- Type F only/ do NOT use Dexron/Mercon

--------------------- Ford code "y" for trans in 68-70 Mustang/ last # on VIN plate Type