The only issue with swapping brakes from shaft to shaft is the drum.  The centering hole is smaller on the narrow axles so if you put the late model brake setup on an early axle, it is impossible to center correctly.  Brainless did that but he had a set of spacers made up that center the newer drum on the old shaft.  I stil say get your but over the hill and Ill hook you up with the parts you need.