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I think your S.O.L. if I remembler correctly most of the drum brake D44 axles had six bolts bolting the caliper mount and spindle to the knuckle and your 94' TTB has five, also on the newer front ends the caliper mount is cast as part of the knuckle, if your 75' front diff is an open knuck housing & you feel like experimenting you could see if you can put the entire knuckle from your 94' on the 75' housing (from the ball joints out,) I cannot tell you this will work for sure, I've never tried it, even if the 75' has the five bolts holding the spindle on you will have to find caliper mounts & calipers, if the 94' knuckle assembly will not fit the older diff your best bet would be to find a late 70's diff that already has disk brakes,
94 knukles wont fit the 75, sorry. But if I remember correctly, my early/mid 80's broncos have a 6 bolt spindle pattern that looks very close to the 6 bolt drum brake pattern, so maybe the 94 has the same 6 bolt pattern seeing as they are the same general suspension.