I've read this post several times and am a little conflicted on what advice to give.

One side: It is a stockish, pump gas 383 probably in a 3900 lb car pushing 100 mph in who knows what atmospheric conditions. Conclusion: not bad.

The other side : A 383 as you described only pulling to 5100 rpm. Conclusion: something is not right. If your buddy's car is noticeably faster and everything else is about the same, that kinda supports this conclusion. What rpm is he pulling? Maybe do a detailed comparison between the two and see if his verses your performance makes sense.

If it is really falling off at 5100, that is not right and you should look in that direction. Ignition box replacement is probably a decent first step. Next is fuel delivery. Best test in my opinion is an inline pressure gauge near the carb that you can read at WOT through the rpm range while driving. I think you should have at least 3.5 psi, or so.

Twice I've had mufflers fail internally that just suck power away big time, but you never know it. The only reason I found it was because I was going to the track regularly, and I lost 3 mph between visits. FWIW, both times they were Super Turbos.

If that is not it, maybe your lifters/valve train are not keeping up with the high rate Voodoo cam.

And to your original question, I think that a solid lifter cam is always a good choice if you don't mind the clatter. Kinda eats away at that stock thing though.