I have run a lot HEI's on my distributor machine, I adjust the end play for .010" - .020" or enough for oil get into and around the bushing. The bushings are not a standard size, I order them for a High Performance Buick shop for a reasonable price. You can add 1/2" ID machinery shims or make your own, most of the time I knock the lower bushing out and replace it with new. I have seen them with the pickup coils way off center and still run OK, but I try to center them best I can. With the lower bushing out, it's easy to knock the upper one into place. With a good puller. you can get the bushings out and reuse them if you have to. The OEM lower thrust washers wear, so be mindful of that when cleaning and align the dot on the gear with the pointer on the rotor.
