Hey B., I'd have to go dig out one of my Edelbrock carbs to be sure, but don't they have idle circuit adjustment screws? Open them up and you get more fuel, not just at idle, but also during non throttle cruising. As for the vaccuum leak - start it up and fog some starting fluid around the base of each intake runner base, if it perks up you found your leak. You also don't need to change out the needle valves(?) just put lighter springs in - nice thing about that style, no jets to change. Get a 1" phenolic spacer on there with a heat shield and make sure your fuel lines are routed well away from any heat source. On top of that you could booty-fab a cold-air intake out of some 3" rubber hose and a K&N bullet style air filter. Combine cold air with non-boiling fuel (and more of that fuel) and those large pistons and you can forget about pre-iginition problems. personally I'd crank the timing back up to 10-12* as that fat piston gives you a larger area to have to ignite the mix. And get all of your timing in by 2k or so to take full advantage.
On a big block even you cannot hurt it too much by tuning it up a little. Apply semi-hot sb standards to a bb and you're just getting it in tune.

Ron