I'm restoring a 1990 dodge D250 for working and towing. I have a second identical truck for parts but both have different differentials. One has the 9-1/4 with I think 3.90 and the other has the Dana 60 9-3/4, I don't yet know the ratio. What is the best choice to use for towing trailers & such?

 

The Dana 60 is the heavier duty of the two and has free floating axles. Which is best depends on the ratio of the 60.