Iwas doing some other work and I checked the shop manual. There are two pages in there on the timing of the 80 and two more pages on the timing of the 18-27/18-28 tractors. According to the book the one you are working on has only one timing mark(TDC) and the impulse for those Bosch mags is different. Send me an e-mail and I will photo copy those two or four pages for you.