I have being dealing with the play of stock kind vacuum advance plate and non concentric advance circunference with the reluctor since ever, because I have found my reluctor bite by the pickup coil in the past.

I solved ( somehow ) the advance plate play with teflon tape to the pivot shaft between pickup bracket and plate hole. This saved a bit this play for a more consistent gap when advance plate moves.

About the non concentric advance movement must say, sorry, but is IMPOSIBLE to draw two circunferences with a diff center ratio. The advance plate pivot is way out of the dist center shaft, hence distributor/rotor, so the pick up coil will NEVER be parallel to the reluctor allong his travel. What I did is bend here and there the pickup coil bracket to get at least .002 to .004 variation with and without advance. I could get .007 on rest position and .010 with vacuum applied tweaking the coil bracket at dif points. The rivet to the coil bracket plays a lot on this, but once adjustment screw is tight is not a problem anymore, but while getting the gap it could become on a headache. You could remove the existant rivet and install one tighter.

About distributor. MP/Mallory piece is quite good with the adjustable mech advance and diff springs options, but with same stock dist issues. Rotor is also indexed around 90 degrees off, so will need to set it off the same the oil pump shaft if you still want to meet the #1 on cap just like factory did.

Firecore distributor has get good comments, but as far I have seen is more of the same. The only diff is really the bushing is serviceable with a removable assembly cover, but, how many times on your life will need to really replace the bushing? Even less on a Small block! Big block units require more attention on this. I can't tell if the advance plate and coil bracket play has being corrected thought with more precission cuts and assembly. But still if this has been corrected on dist plate, when times come to replace the pickup coil, pivot shaft thickness will be ANYTHING manufacturer made, getting back the plate play... unless you replace JUST the coil and magnet bracket assembly reusing the gap adjustng plate where it mounts