So a trigger wheel type deal. I’ve thought about calling in a favor to a machinist friend and having him cut slots in the hub of the crank pulley. Seems like some math could figure out size and spacing relative to the flexplate.
My original plan had been to cut slots in the pulley as well. In the end, I was worried about the scale of the slots, wasn't sure if the PCM used the leading and trailing edge of the slot for anything. As I remember, I scaled the slots in my ring to match so that (in theory) the PCM would see the same number of degrees between the leading and trailing edge. Seems like slots in the pulley itself would have been pretty small.
I went to the junk yard and found a motor on the ground and used that to get an idea of where the slot was in relation to TDC. I think the trailing edge of the slot was at 10 degrees ATDC, but I would have to dig out my notes to be sure. I had a friend that was doing a Magnum swap on a TJ so we mocked up the parts and welded the ring to the crank pulley using that relationship.
