So… I got the alternator mounted and it looks like I may have to re-think the current configuration. Slight pulley alignment and possibly limited adjustment… but on the plus side.. it now clears the frame rail.
The trucks original trans crossmember was cut in the middle to make way for the TH400 so the plan is to have a removable support brace to take the load behind the leaf springs. Using what's left of the original drop brackets as the base.