Rod,

I've had some success running a vaccumm advance using the crane Adjustable diaphagm dialing it pretty much all the way out, but that was on a 4 speed car.

a blower drives about like a n/A car until you nail it (motor can't make boost until you give it enough air) but once you do you don't need a ton of advance because the cylinder pressure is much higher at low rpm than you can possibly achieve N/A. Drivability is great once you get it sorted though....especially on misty mornings with a little coolness in the air.

I would definately consider a methanol injector like MrYuck runs on his sixpack 440, I see no downside to that at all.

Trans line pressure, never gave that much thought because I always ran MVB's or 4 speeds.

I like the Dyers supercharger set-ups, manifolds need a little port match and clean-up but nothing special. I ran a 383 with a V6-71 and only the 2" belt drive back in the early 80's that worked really well, the standard 3" drives on the 6-71 and 8-71's always seemed to do well, fatter belts/drives can play havoc with radiators and cooling in terms of fitment. A lot of people used to run their belt tensions too tight which adds a lot of strain to the bearings and crank snouts. Too tight will cause the belts to want to walk, and it's not only tension it's parallelness that also comes into play.

I used to put a few drops of Pro-blend in the gear oil, it seemed to cut the friction down a tad because the whine changed pitch slightly ( but noticably)

Like I said HEAT is the one thing people probably don't realize about blowers, once you run them hard you can actually start losing a bit of power because that air builds up a lot of heat. 600 hp also makes a lot more HEAT than 400 hp, how you wick it away is important if you want it to live, that's in part why I like a bit of a wider valve seat on an endurance street blower motor, it gives just a bit more area for heat transfer (since any goven valve is closed well more than 1/2 the time) from the exhaust valve back into the head/cooling system.