Maximum lift with stock J heads

RustyRatRod said
If someone gives you an across the board answer, that's inaccurate. This is how it is. If you want to know an exact number, you have to measure retainer to guide clearance on what you have. I've seen some go as far as .520 lift and as little as .470. That's because Chrysler was not consistent with the heights of the guides. They're going to be different head to head. So measure.

FWIW: Mullen’s recommendations have been accurate for me, so far.

RRR has a point, always verify. By now, most heads have been worked, and the valve seat may be on its second vale job.

increased retainer clearance effects the spring seat pressure that your camshaft requires.