You just roached your trans and you're asking about more hp/tq?
Not sure who builds 68RFE trnasmissions but pulling 17k+ may warrant a built trans if you plan on putting alot more "hard" miles on towing, and certianly if you up the power. 'Cause then you'll just put more power to the trans and kill it quicker the next time.
6% grade you were on doesn't sound bad, especially at lower speeds. Shifting back between high rpms in 2nd and low rpms in 3rd you were at what, about 30mph?
Locking out the upper gear would definatley helped. If you had a egt gauge you would have really wanted to lock 'er into high rpms as well, likely.
The 68RFE in a '09 is the same as your 07.5, all the way up to current models, essentially. You can now get a new HO Cummins 850 ft lbs (vs your stock 650?)with the Aisin trans. It's all a matter of if you intend to keep the truck a long time or not. If I was towing that kind of weight regularly I'd drop the $5k on a good built trans and get another 200k out of it.
