Brain, I bet your car would be in the 5's easy if you were to use a rev limiter at launch along with the transbrake. Most guys I know of that run in pro box class, leave at around 4500, and usually shift around the 7000 mark. (bbc's) If you have any weak links in your drive line thats a sure fire way to find them. I personally dont care to run in that class so I almost always footbrake.
Leaving without a rev limiter or transbrake (footbraking) most say they slow down at least a tenth or more.
Switching to alcohol usually picks up slower cars more than faster one's.
One of my friends at the track swicthed his 540 over to a alcohol and he only picked one number and it cost him roughly a grand to make the switch so it wasnt a cheap tenth. However not everybodies car reacts the same to changes, another friend switched his 468 from a 1050 gas setup to a rons toilet alcohol injection set up and his picked up three numbers.
When you described your motor combo I was shocked, thought you talking about mine. I am building the same motor but with iron merlin vr 345cc heads. My 69 camaro is little lighter but I will using a much smaller 33x10.5W tire, with 568 rear gears and a 1.76 powerglide. I hope my numbers will be close to yours but it will be atleast next spring till I find out.
Goodluck, Charles