Yes, H is 130, generally what I go with. Factory speed limiter is 105, if you're stopping at 90 there is something amiss. Those headers look like a Pacesetter rip-off. The most popular long tube for our trucks for years was the Pacesetter 72C2211 (I have a set in mine) but I don't even know if they make it anymore. Tuner any Superchips model 3865 or newer or Diablosport 7137 or newer.
A 6.1 will bolt in and you can mount your front cover and accessories on it however your RFE's will live shorter lives, even with the stock 6.1 cam. Unless you mean a 5.7 or 6.1 stroker, you cannot run a VVT engine (which is what a factory 392 or 09+ 5.7 is) in your truck..............................unless you are willing to go standalone engine management. It has been done. There is a 2004 quad cab with a 6.1 based 392 hooked to an 8HP70 running around using a Holley standalone. I've talked to the guy at length (mainly about the ZF swap) and it is definitely not easy nor cheap.