Though the GMC 1/2 ton has a softer suspension, I went with 800# bars at first and found it did a fairly good job. I bought some 600# bars on eBay for about $60. I think they may do a better job. Given that your hitch weight is less than 800#s, I'd also consider the 600# bars, particularly if you are using the dual cam sway control.
Computers manufactured by companies such as IBM, Compaq and millions of others are by far the most popular with about 70 million machines in use worldwide. Macintosh fans note that cockroaches are far more numerous than humans and that numbers alone do not denote a higher life form. -NY Times 11/91