UPDATE! Made it to the dyno!
Finally made it to the dyno at Wicked HP this evening. HP was peaking at 5700 rpm and dropping off from there, exactly as it felt. Made 356hp/358tq N/A and 458hp/485tq on a 125hp nitrous shot. Before i went to the dyno I locked the distributor at 36 degrees. After a couple of pulls I found that it made the best power at 38 degrees. After all the passes the only two things that the shop thought might increase those numbers with my combo was to port the heads or try shimming the valve springs to see if it helps. Given my setup they thought it should peak at 6400 rpm or higher. I think I'll try shimming the valve springs since that is relatively easy. I know I have a lot of room on these springs before they would bind. Anybody have any other ideas?