I don't know if this is your problem but when I replaced my vacuum wiper motor with an electric one from LMC, I also got a linkage problem that I couldn't correct with blade positioning. I can't remember the symptoms exactly but it seemed that one arm was too short.

See the picture. I cut a piece of metal and put 4 slotted holes in it for adjustability. I then got brave and cut the arm and put round holes in it. Turns out that lengthening that arm solved the problem.
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Adjustable wiper arm.
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1948 3/4-Ton 5-Window Flatbed Chevrolet

34 Years. Now with a '61 261, 848 head, Rochester Monojet carb, SM420 4-speed, 4.10 rear, dual reservoir MC, Bendix up front, 235/85R16 tires, 12-volt w/alternator, electric wipers and a modern radio in the glove box.