Help! Rebuilding by 66 dart but im putting in a slant 6 225 bored out to a 227

Just out of purity or part specific to the manufacture quality?
Yes, I am for the most part a purist. In regards to quality, yes. But quality depends on the parts you are buying.

Bottom line, Chrysler designed one of the best electronic ignition systems ever built, with millions of miles to prove it.
It just flat out works, and works very well.

And lastly. Every GM hei system I've seen installed in a Mopar looks like AZZ.