A big block bud scored a P3690426 kit distributor http://store.summitracing.com/partde it appears to have the newer set up. So no more welding up the slots to limit the mechanical advance?

Yes and in fact the only BIG diff with stock unit is really the mechanical advance is now adjustable... rest is basically same dist

Being same dist than stock units then you are getting same new CHEAPY CHINA MADE INTERNAL COMMON REPLACEMENT PARTS like the reluctor and pickup coil, that does need to be adjusted/touched to get a propper "precision" parts.

I had to mill down every reluctor point to get the right gap... then BEND a little bit the pick up coil assembly to get a decent gap too on vacuum advanced position, and then readjusted again the gap on rest position... had to made that three times to get a good .007/.009 gap average in both positions.

If you only check gap on rest vacuum position, pretty sure coil will bite reluctor, because pickup coil movement IS NOT propportional with ratio againts center of dist

also milled down a little bit the pickup coil point to get a decent straight sensor point.

That's something you don't expect to make on a Mopar $180 unit, BUT HAVE TOO. If you don want, then spend double on an MSD ready to Run dist ( I mean with vacuum one ).. or maybe another aftermarket performance dist. Dunno if rest of dist options are more less with same issues. pretty sure MSD won't

I have purchased two MP distributors in the past couple of years. One had the billet housing without a vacuum advance and the other is a vacuum advance unit. I can't commnet about where the parts come from, they are made by Mallory so if Mallory sources parts from China then I would guess these would have Chinese parts too.

As far as reluctor to pick-up alignment in both cases they alignment was very good. The billet unit didn't require any adjustment. The vacuum advance unit had the gap set wide and came with a little instruction note stating to set it to .008-.018" gap. Once set the alignment an prepedicularity was very good, better than the orignal factory distributors I have seen. Certainly no reason to file or touch the reluctor.

Personally I like the fact that it uses stock cap, rotor and pick-up parts, makes maintainence much easier since those parts are available at the local parts store.

how much time ago was that ?

I'm not against the stock parts used what I like a lot and in fact I want to keep the car "stockish" as posible, but just talking about quality and assembly precision... just giving my experience