Towing with a 3.73 F250 6.2L, will a 4.30 axle help ??

A cheaper alternative might be to check junkyards for a wrecked truck that you could just swap the axles out for. I drive a 2012 F250 with the 4.30's for work. My V10 with 4.10's will still pull better than it does. Bottom line, the 4.30's will help, but the shift strategy on these newer trucks is to get in the highest gear possible in the shortest amount of time which doesn't lend itself to low-end pulling.