Use or don't use vacuum advance on distributor???????????????????

It's also interesting in that Chrysler had ported vacuum in the 50s on the Hemis. So the conclusion that it was only pre-cat fix is BS as far as I'm concerned. If the engineer in question could be verified I'd feel better about the explanation. I don't see it as entirely plausible given the reality of it's use decades prior to invention of convertors. But that's just me...