First verify you have adequate fuel delivery and the proper valvesprings in the motor. As you desribe the 383 is should want to rev to at least 5800 even with manifolds. I lije solids in 383's and 'generally' anything that makes a comparable 340 quicker will make a 383 quicker as well. What that means is, treat it more like a small block in terms of tuning.

Id like to run a solid with about 232/238 @ .050 and ~.520-ish lift on a 109-111 spread in at around 105 since you want to 'use it up' with a relatively low 6100-6300 rev cieling with the manifolds. Combined with a fairly tight 9 1/2" or 10" converter. That would shave about a 1/2 second off your times and the car will be more fun to drive as well. the cam will have a wider powerband ( come in sooner and stick around later) .

383's are fun and make good power, you just got to get them to the sweet spot quickly and let the revs do the rest.