Thanks Bill, this truck has the E4OD so the rpm's aren't that high. The biggest jump was when I put the temporary axle in and it went from 308's to 355's then I drove it like that for a bit over a year. When I finally swapped in the 373's it didn't seem all that different but then I was also swapping in the posi at the same time. The posi steals some hp so the gain of grunt seemed negligible, that and I had initially set the brakes too firm whoops! It's been a little while since I drove it but I think I was running 2500-2700 at 70 compared to 1900 with the 308's