I have a 40ft enclosed trailer which weighs only about 8000-9000lbs.

The bigger problem is that I am always driving 75-80 and would sometimes like to go a little faster.

They just installed a new converter (warranty) at 29k kiles.

I am running edge normally in stetting 2 when towing and 3 when not.

Now my question:
I will never buy more then the edge/juice combo but I would like to tow on 3 and maybe drive around in 4 or 5.

What kind of tranny/converter upgrade would be needed not to break it all sooner or later??
Normally only keep any truck 2 to 3 years (have it for 1 already) so I would not like to go "all out"
What would the approx. cost be for whatever I need installed (located in S.Florida)????????????

Truck:
04.5 3500 dually, 2wd, CC.
Edge/Juice 4" exhaust and airintake.