I would either get a towing cam, what we used to call an RV cam, or call Vinci and get a custom cam ground for it.
As for swapping the heads, I'm not 100% sure about the 5.3 heads on the 6.0 block... back in the old SBC days you could put the 305 (5.0l) heads onto a 350 (5.7l) or 400 (6.6l) to...