Running a 455 in my 74 Cutlass with the Edelbrock Performer. I would like to convert over to HEI but I hear the vac advance on the HEI interferes with the intake making timing adjustments an issue. True? Maybe Pertronix is the way to go?

 

A HEI distributor fits fine. No clearance issues at all.

 

I dropped an HEI into my '66 425, and it had a slight clearance issue with the intake, but it was easily enough to remedy by rotating the distributor a bit further and then offsetting the plug wires either 1 or 2 spaces to put them back into the right spot for correct timing.

From what I remember, the vac advance wasn't the issue, it was one of the bosses for the cap hold down, or the plastic cap itself that interfered with the intake, but other than that, it worked beautifully.