The only problem with setting the initial timing for max vacuum is that it does not take into account the total mechanical advance the distributor is capable of. You could wind up with far more than the 36 degrees total timing that is the norm in the SBC and run into detonation. This is why it is important to test total timing with a dial back light after setting the initial. If you need more initial than stock, that is fine, but you will need to find a way to limit the advance mechanism from delivering excessive advance at it's maximum point. Some aftermarket distributors used bushings to limit the travel, and some people epoxy the slot or weld it up a bit to limit total mechanical advance when confronted with this situation.
