4BT or 6BT is a very simple question, sorta. If you want maximum power and decent mileage then of course 6BT. If you want plenty of power, about like a 360 4bbl, and mileage that people think you're an outright liar: 4BT!

My Town Wagon 2WD, 4BT/NV4500 4.1 gears: Driving at 70-75 MPH with a 60 mph headwind, in a fair hurry, for about 400 miles, then returning with about a 50 mph quartering headwind, then hitting snow, ice, sleet, rain, more snow, and about 100 miles of that driving was through steep mountains on winding roads, average mileage 32 MPG. 6BT would probably be about 20-22 MPG on that trip.

I have no trouble towing with the 4BT. Truck filled with steel & machinery at maybe 7,500 lbs, with a Chevy LUV tagged on behind with more steel & machines, probably 4,000 lbs, couldn't even tell the Luv was back there.

Main problem is the price of 4BT's is scooting up, everybody wants one!