well I am pondering getting 4.10's. they are relatively inexpensive and i will be doign myself. i also will be putting in a b&m trans cooler and will do the j mod soon as well. how badly will the 4.10's affect my gas mileage, i do alot of highway driving which keeps me on the interstae over an hour a day. also if i run a supercharger in the near future will i have to swap from 4.10's to 3.73's? also, i might have a line on some PI heads for 300-400$. I know the NPI heads outflow them when P&P'ed, but 400 is a hell of a price. what do you guys htink?