Vacuum gets disconnected from the carb, plug it at the carb. You should have around 36 degrees total mechanical advance when all said and done (vacuum disconnected). But most folks find that the small blocks like a lot of initial timing, as much as 20 degrees. This messes up the total mechanical advance (you'll have too much), so you have to dial it back by adjusting the distributor. I run 18 degrees of initial timing, with my total mechanical advance limited to 38 degrees.