I have read all the responses to your original question and since what you seem to want is a change from the 3.54 ratio commonly found in the Dana 60 to something lower, it would seem that the best and cheapest way to do the job is to to mount a larger overall diameter tire on the car to effectively change the rear gear ratio to what you want. After all you are going to tub the rear. When I built my '68 Coronet, I tubbed it and built wheel tubs from sheet steel that were 40" in diameter and with a 4:88 gear and L78x15s I could drive it on the highway

Did I miss something??