I'm a late arrival in this thread. I usually stay away from "blower" stuff... Too many opinions. Very few pros. It's obvious here, who's who on this site for blowers! My compliments and my thanks. I learn from Jester and Cobalt every time I read something they write. Everyone else, of course. I just had to point that pair out. Good stuff!
I have input. First an observation then a question. Your gear is still too "low" (higher numerical). BBCs with small blowers (what's your ratio?) make torque like big N/A Pontiacs. RIGHT NOW! Take advantage of the massive low-end and gear it "up". We use 3.90s for 461s in cars under 3,500 lbs. and 1/4 mile. That MIGHT be a little stretch, but 4.10s are certainly correct. With a little shorter tire, the "top-end charge" with 3.90s will significantly improve MPH, and usually a corresponding improvement in ET. The idea with a "torque" motor is to "short-shift 1-2 and maybe a little 2-3, but "let 'er eat" in 3rd. Which leads to my question...
Why are you limiting the RPM of a short-stroke BBC to 6,000? 427s are "safe" at 7,000 when you upgrade the rockers and distributor, with stock "everything else". With the small amount of boost you have, good forged pistons and good factory rods are "up to the task".
A nitrous cam is WRONG WRONG WRONG for a blower engine. Sorry, but it's true. You're pumping mixture out the headers... Too much overlap. Nitrous engines "like" it for the scavenging effect. They also generally have longer duration on the exhaust side than "blower" cams. IMO, with a Roots-style blower, you really should have a blower-specific camshaft. You can "adjust" the duration and lobe centers to suit your RPM requirements. We use Comp exclusively for this. They have good engineers. The valve train is the LAST place to "scrimp" when building a BBC. You need the good stuff.