Timed or manifold vacuum advance?

I'll have to ask Don at FBO sometime why he insists you use manifold vacuum instead of ported with his dizzy's - although talking to him can be a challenge in itself.

Yeah, I get that sense from reading his book. And I'm not impressed with his ignition system, either; when I get time I'm going back to my standard HEI upgrade with appropriately dialled-in mechanical and vacuum advance curves.