The following is what I do to set up a Mallory dual point dist on a 59AB engine. The Mallory distributors I've been seeing the last few years are coming from the factory with the centrifugal advance stops set for about 41-44 degrees centrifugal advance! Add in the typical 4-8 degrees initial advance and it gives anywhere from 45 to52 degrees total advance. Way to much in my opinion.
The typical street FH will not tolerate total advance in excess of 21-22 degrees. I readjust these advance stops to limit the centrifugal advance to 17-18 degrees (note: the electonic dist uses the same centrifugal advance setup and can be set up the same way).
Remove the breaker plate. See the two torx head screws holding a plate down? Notice there are two slots with tabs in them. These tabs are adjustable to limit the centrifugal advance. Mallory makes a set of "keys" to slip in these slots to adjust the tabs against. Good idea, but the keys are pretty expensive and aren't all that accurate in my opinion. Loosen the two torx headed screws slightly. Now use a 0.070-0.072"" feeler gauge (BillB uses an allen head wrench 0.068" wide across the flats since his feeler gauge is too wide to fit into the slot) and position it in the slot. Slide the tab up against the feeler gauge and tighten the torx screw. This will limit the centrifugal advance to 17-18 degrees. Since we want the total advance to be in the neighborhood of 21 degrees, this much centrifugal advance should not promote pinging (detonation) at 35mph and up. Do the same with the second tab and torx screw. Reassemble the dist plate and adjust the points. I set both sets of points at 0.021" using a feeler gauge. Reinstall on engine but only snug the two mounting bolts down since you want to be able to rotate the dist to adjust the timing. Start up the engine and warm it up.
Hook up a vacuum gauge and advance the dist until the vacuum gauge shows the highest reading possible (I use a long screwdriver and hammer to tap the dist around.... be careful since there are fan belts and fans to reckon with). Now back the dist off until the vacuum gauge drops exactly 1" of vacuum. This is where your engine and mods are happiest. Tighten things up and you're through. I don't use a dwell meter unless the dist has a lot of wear on the shaft and/or bushing. I think feeler gauges are all that's needed for the majority of driving (exclude Bonneville, roundy-round, and all-out drag racing).
I've checked a few of these on a dist. machine after I've set them up as I've described and found they were within a degree or two of the recommended dwell.......