timing?

Pump gas strokers generally do not need as much lead. Reason being a long rod long stroke hits the "sweet spot" in terms of rod/crank geometry faster. The reason there is any ignition lead is so the piston is at the right spot when the burn produces maximum pressure. Different fuels burn in more or less time, and oxygenated pump unleaded with Ethanol burns very quickly. So too much timing can "waste" that energy by peaking before the rod and crank are in the best position to use that leverage.

If this is a drag race only car, then fixed timing is fine. Run a quality fuel, and vary it by 2° increments until it slows down. You'll find the best amount of lead through repetitive testing that way. That's also why you use the log book and weather station as the perfect timing will vary depending on atmopspheric conditions. Testing for vacuum at idle doesnt help, nor does holding a steady rpm off idle and lookign at vacuum levels. The only way that would is if you were at full throttle.

If the car is driven ont he street for any length of time, IMO, it should have a properly curved ignition to take advantage of the light and part throttle situations that street driving has. Vacuum advance will give a lot better mileage, better part throttle response, and does not affect wide open performance at all. So whenever possible, I do run the vacuum. But, eventually there isnt enough adjustment in the can to cover the lower vacuum signals a big cam has and you have to scrap it.