Welcome to the forum. I don't know much about heavy towing, but I can tell you that I think you've come to the right place for your question. The participants here were a great help with my purchase.
After spending last summer/fall shopping for and purchasing my truck conversion, I can say that I think your price range is reasonable, so long as your expectations for newness aren't too high. You can get the power, but maybe not the glitz at that price point. Best of luck!
2006 Renegade/Freightliner Coronado 43', Detroit, twin screw, 12spd
2001 Ford Excursion PSD
2017 Ford F450