Basic Alternator Dimensions
Any substitute alternator must fit in the limited space in front of the head.  There is only about 1/4" clearance behind the stock early Ford alternator and the head.  

A slightly different distance from pivot to adjuster boss should not present a big problem.

We can deal with most wiring arrangements of aftermarket units with the appropriate schematic, which you must supply.

Alternator dimensions
Stock Ford Alternator