My own 2c - With a stock pump and turbo kit(any), you are looking around ~200 HP at the wheels max. That's probably 260-270 at the crank, which is about what Banks advertises.
You'll probably need an upgraded IP if you want more than that; plain and simple. RD2-110 will net you 250 RWHP with a kit turbo, and probably around 300 RWHP with a better turbo setup(CDD, R&D etc).
Personally, my DD's just got a worn IDIT motor, WW2, stock pump cranked, 4.10s and a 5-speed with GVOD... she probably makes around 180 RWHP.
It's both plenty and not enough - towing a 3K lb flatbed yesterday at 70MPH, I'd go between double OD(equivalent to 5th with 3.55s) and OD; maintaining 70 wasn't too hard.
Towing a decent load back(I'm thinking about 7K on that trailer, so total of 10K), I was in single OD, and had to downshift to 4th occasionally on hills. Maintaining 60 was easy, 70 was really pushing it(~900-1K EGTs in 5th at like 2500 RPM on flat-ish ground).
I've also towed ~14K behind me; it takes a bit to get to 60, but is very easy in the 0-40 range for back roads.
It's very much one of those things where once you get to speed, it's not hard to maintain, but going from a stop requires winding her out in every gear.