Because boneyards around here don't have slant sixes in them.
I have a lean burn one on hand, no mechanical or vacuum advance at all. It's part of my EFI upgrade, going to have the computer handle timing. That one you cannot do the shaft swap trick on, which is why I already had a plan to address that. Essentially, I am making a shaft extension that's use the stock /6 roll pin to hold it on. Only reason I am even messing with the /6 version with advance is because I am tired of the new made points rubbing block wearing out and the EFI swap goes on the 230 I am building. Less than 1500 miles on the new points and the dwell is at 20 degrees. Plus it was Sunday when I was messing with things adn Napa wasn't open, only place in town that has the points in stock. So I thought "hey, perfect time for the conversion", lol. This way I can use /6 cap and rotor, don't have to worry about finding NOS points, cap or rotor anymore.
Oh, one other difference between the new /6 distributor and an original, the bolt that holds the timing tab to the distributor is metric. Got to get one.