1970 Chevy C20 sluggish and bogs out?

[1970 C20 Surf Wagon]

I have a 1970 Chevy C20 truck w/ a fresh stock 350, headers, electronic ignition, new plugs, wires and alternator. It ran and sounded great for about 500 miles. All of a sudden it goes from roaring to puttering, I cant give it too much gas cuz it wants to stall. It feels as if its starving for gas but the clear filter is full, the gas pump is new. One of the funnest parts about driving the truck is its fast starts and great sound with dual exhaust all the way to the rear. I hope some one has ideas for me to try, it has a older Q-Jet that was rebuilt about 5yrs ago.