I think the best thing you could do for your engine is to install a Gear Vendors over/under drive. You've got plenty of HP and the torque ain't bad, but that 4R100 4 speed just don't have enough gears to deliver the power where you need it. Think about it - aren't you doing fine rolling down the road? And I doubt if you have any problem getting it rolling from a stop. It's the hills and the mid-range accelleration that usually leaves you cold. More gears in the middle will let you stay in the sweet spot and apply the power when you want it. Costs about the same as the Banks kit.
http://www.gearvendors.com/
Don't get me wrong - I'm a Banks fan. Had the full kit on my 96 Southwind 36 (Ford 460) and it helped there, but I still ran out of oomph on anything more than a mild grade. And the V10 gets less benefit than the 460 did, making the gain for the dollar lower. Have not bought the Banks for my GM 8.1 because nearly all the gain comes at RPMs where I won't get to use it anyway, i.e. well over 4000.
Gary Brinck
2002 Dolphin LX - WorkHorse W22 chassis
2000 Chevy Tracker 4-Dr 4WD
Homebase in the Ocala Nat'l Forest near Ocala, FL