I wonder how much of a gain I will get!

My 440 dart I picked up seemed a little flat on bottom,it pulled ok but not a big tire roasting monster, I start checking it over yesterday and find that there is absolutely no timing advance, there must be a hole in the vacume diaphram because you can draw strait through it with a mightyvac tool plus the whole advance plate inside the distributer is siezed up,I couldnt even move it with a screwdriver,got a new distributer on the way:thumblef:hopefully bI will se a performance gain!