The towing duty throws a wrench in the equation. Towing means your foot needs to be opening the throttle further , which will put you into boost. Possibly all the time. It is hard to design a gas burner for continuous boost.
For the regular driving.
Turbonetics 60-1 T4 .8 ish exh housing with a P-trim wheel
The towing may require a looser exh housing such as a .96 or larger.
