dyno #s seem low ?

Took my 71 340 duster to get dyno tuned, end result 271 HP & 277 tq on a dyno jet. This seems pretty low to me, I was looking for a little over 300. Mods are ld340 intake, voodoo cam, 650 quick fuel carb, headers, 2.5" exhaust, fbo ignition, stock J heads. Do these numbers seem right?? Motor was just rebuilt to factory specs 2k miles ago.