The 7.3 was built as a work horse. Nearly every school bus, trash truck and dump truck from the era had that engine, either from Ford or International. I loved mine, but it did need some "enhancements". 275 HP/520 lb/ft was good for the time, but not enough for towing bigger trailers. I also had a 2001 F250 and did nearly everything you are doing. FWIW 400/800 is about the best you can reliably do with a chip/exhaust/air box. To go higher, you need to drop in bigger injectors and that gets expensive.
I already mentioned the intercooler boots. The only problems I have from chipping mine up was beefing up the high pressure oil side of things. The fuel injectors work off oil pressure on the 7.3. Chipping the engine puts a lot more load on the high pressure oil side of things to increase injector cycles. Look into getting an oil rail crossover. On the stock motor, each head has it's own oil rail. The increased duty cycles put a lot of increased stress on the oil rails by opening and closing the injectors faster. The crossover helps balance out the pressure spikes as the injectors open and close.
Here is a link. Even with this, I blew the stainless braided oil lines. Eventually the pressure spikes cracked the housing on my HPOP (high pressure oil pump), but I was pushing over 450 HP and 1000 lb/ft.
I would probably still have that truck if it hadn't developed electrical gremlins. More HP/Tq than the newest trucks and 1,000 lbs lighter.
j