Well, not as much as it could with cams...

You are probably a little further ahead than most, you have dual exhaust and an aftermarket intake. Still if you think about intake pulses and manifold loading your smallish valve lift and duration is hurting the most. It might give you a little boost, but nothing drastic. As it stands you have allieviated a couple of the many intake/exhaust restrictions.

Just as an FYI, a small block Ford that I am building started with a 400cfm 2Bbl carb stock - 160 Hp. Here is what I have changed to make 600cfm necessary:

Higher compression ratio - 8.6 to 9.2
Bigger valves - 1.5" int, 1.3"exh - 1.7", 1.5"
Full Port, polish, bowls and combustion chambers
Bigger cam (492 lift, 268 duration)
Headers (full-length) to dual 2.5" exhaust
Intake manifold (to accomodate) and 4Bbl carb.

As it stands finished ~250 hp.
If It were carb only ~ 180 hp.

Do it if you want (I have seen your truck with 35's - I am sure you need the power too), but I will make more of an effect if you can scrape together more clams and buy the cams too.