It's been a LONG time... Need some new advice

So, it's been a LONG time since I've been on here. I did a lot of stuff to my truck "back in the day", still have the same truck, running strong.

Here's the deal - I tow. I only drive my truck when something is on it or behind it. It's an '01 F350 7.3L Dually, with 75k original miles.

I want to tow better. Durability is a must of course. Now, I don't want to go so nutz that I ventilate my block pulling a mountain pass. But, mileage is secondary to performance, within reason.

My camper and car-trailer weigh in at about 21,000 GCW. I pull all the big passes around here at about high 40s low-50s. I watch my gauges religiously when pulling a hill. MPG when loaded pulling hills around here is around 9.

Here's what I have (Keep in mind, all of this is 10+ years old)
Superchips 1705 -- set in 110hp/Race since day 1 (it will be the first to go)
4" turbo back straight pipe
Jasper Transmission's 4r100 MonsterBox - back in the day, it was the only "worthy" alternative to a BTS tranny (if he's still around.)
Tru-Cool Max tranny cooler
TC Manual-Lockout mod
Standard 3-gauge pillar pack, pyro, tranny and boost
K&N
Royal Purple in everything
To this day, I do not know for sure if I have PMRs or not. Never pulled the pan.

What's new and improved?