I think I have an idea to make the flywheel I got work, it’s odd that all the used flywheels I find (almost all w201) don’t have any timing Windows.
My plan is to pick up a w124 flex plate, line up all the crank bolt holes and bolt them together, mark the flywheel, measure the distance between the teeth of the flex plate and the top of the windows, and cut the windows off the donorflex plate and weld them on to the flywheel since is doesn’t have any windows on it currently.
On BMWs if this era they had similar spots on the flywheel, they were just smaller, I had one come off on a gray market e21, I was able to find where it went, drill and tap the hole and with red locktite put a bolt in its place all while the whole car was still together and it ran perfect after.

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1989 Mercedes 260e
1972 GMC shorty van
1982 Harley Davidson Ironhead