whew. thats alot for a 1/2ton. but at the same time i wouldn't want to pull it with a 5.4 f250 either.
you can do a couple small things to help keep the trans in good shape. definately invest in an aftermarket tranny cooler. get the biggest one you can fit in front of your radiator. should run you 70 bucks or so.
the other thing i would consider would be a shift kit, trans go or something. that'll also be pretty cheap. that will help keep the trans from slipping under load.
aside from that, you might want to think about getting an aftermarket torque converter.
fwiw, the 99-04 lightnings had the 4r100 in them.