Why are there differences in all of the aftermarket distributors for my 1989 323

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Yes, it's a "1989" Mazda 323. Your year selection only went to 1990.For the last year and a half,my car ran pretty good with a distributor marked D4R86-22 and B6B1 8Y03. I ordered an M-36 Richporter distributor from All Automotive that was to be a direct replacement. It didn't work, due to the usual subtle differences my mechanics and I have found in the past. Do I re-build my old one? My last 8 VIN #'s are K0387996.My computer # is B6K2. The original Mazda Part # is B6B1-18-200. The plaque on the firewall says Made in Japan and 8595B. The car was shipped to California. I bought her brand new. She still gets 30 M.P.G. and has 300K+ miles. I just can't dump her cuz of a distributor problem.Any advice. Parts people can't help. I need a Mazda expert mechanic. Thanx, Tim Coulter.