I find off the line acceleration adequate at partial throttle (people move slowly here) and I have only one intermediate gear ratio to cover the 1-2 combination on your 5-speed Torqueshift.
If you are not flooring it off the line, you don't know what you can do with the power you have, and if you do anything low cost to increase peak power, you won't feel it off the line, you will feel it at the top of each gear, when RPM is 4000-5500 or so. And only at full throttle.
Your RV is a big truck, not a sports car. For a big truck, your C has a quite impressive power to weight ratio, but not on a par with modern cars, even economy cars, which might have 80-120 HP in sizes that used to do with 40-60 HP.