i know some newer trucks can be had with a ZF 6 speed but i'm not sure if they have a 385 style bolt pattern like a 460. might also look into an 80s or early 90s medium duty(F700 or such) tranny, i'm sure that some probably came with 5 and 6 speeds, and the engine used in most of those was a 429 industrial engine that should have the same pattern.
