First of all, Welcome to the ORG!!
Now, you are playing with fire driving, especially towing with a programmer and no gauges!! Stop this now!! Order the proper gauges, PM me for more info.
Next your F350 may have 4:10 in the rear diff, and if so 15 is about right, you should be able to get 10-12 towing a 11K fiver, unless you are towing in the mountains and then 8-0 is about right, hard to believe you were doing that good with the V10, if you were you were doing good!!! Now letting the 7.3 breathe will help a lot. Contrary to what is popular on the internet, you don't need a 4" exhaust unless you are building big HP!! The factory 3.5' exhaust is perfectly fine, the restriction is in the factory muffler that necks down the exhaust to 2.5" and then further restricts it by throwing it through an offset muffler!! Replace the factory muffler with a Walker BTM, ($45) from Napa and it is a straight shot 3.5" , combine this with a better flowing intake like the DIY Tymar or the Ford AIS and you will see a big improvement. You need to do the supporting mods before you add more ponies. If you do things right you will have usable power, power is useless if you have to let off the go pedal due to high EGT's!! With my mods I have never had to back off, and even towing heavy up steep grades, no worries. EGT's are controlled by good airflow and better tuning, niether of which you have yet. Here is the order you need to progress
Gauges
Intake, exhaust mods,
support auto trans with a tuned Valvebody
Only now should you be adding extra ponies, and then the only two I would choose from is DP or TW for your tunes.
Good luck and feel free to PM me with any ?
NCH