What joelc79 is saying is that the he451 and he551 from fleece are pricey. But there is a reason for that. First it's a variable nozzle/vane/geometry (not sure which) turbo. Any of those 3 will make the price of a turbo go through the roof. Plus, then you add in that Fleece (a very reputable name in diesel performance) is the one's that MAKE them. Make being the key word in that. They don't purchase their turbos from other companies. They make them all. Not trying to preach Fleece, but there is a reason why they cost that extra penny, and it isn't because they are junk.
Either of those 2 turbos that are mentioned would be great for towing be cause of the variable vane/nozzle/geometry (not sure). Which in essense makes them smaller at low RPM, MPH, Boost, and fueling and then as all of those rise in number they begin to get bigger and flow more air.