If you are already running an off-road pipe then you will not see much gain from headers. Most of the tests I have seen indicate that long-tubes will only get you a couple of horses over shorties. LTs are one of the few mods I regret spending money on. Even supercharged I saw no gains on the dyno.
ProCharger P-1SC, 9 psi, STD 396/383; Uncorrected 388/375; SAE 383/370.
USAF 1969-1996: Vietnam veteran. Aircraft maintenance. ICBM Operations. Research & Development.
Also own: 1997 Harley FXDWG, 1998 F-150, and 2002 Corvette LS1