[FWB]

while i know nothing of the Subaru gear.......if it was me......i would modify it to use the mustang II rack, in which i am assuming the flaming river one is.
the extra welding may be a pain in the arse, but any repair issues later will be less cumbersome with the parts availability.
what spindles are on the car?
you mentioned the tie rod ends get modified for the subaru gear, the question i would have is what other mods need to be done to use the new gear?