The M5R2 that is used in the 90's F150's
Thats good for a stock/ slightly turned up 4bt. If you plan on doing any work to it, you will want a ZF from a 250/350.
ZF5 from 90's f250/f350? You could definitely handle any power, but the ZF6 is enormous and heavy, it wouldn't fit if I had to guess.