The more altitude you toss at it the more of a advantage you gain on a stock motor. A pump gas kit will not do much at sea level unless some changes are made to the motor. On a M1 @ 7000 feet you are looking at around +80hp
With AV (100LL) fuel you can run 5 pounds more boost it is a good option if you can get it cheap.
On a M-1 I did up in 2008 with a external waist gate, squish band cut to .080 and compression dropped 1/2 of a point I am running 10 pound of boost at 2400 feet on AV fuel.
Buddy and I were having a debate on turbos. He said 50 horse is not worth 4500 bucks. That is why I was wondering. I know I want one. Maybe in a couple of years. Thanks for the input.