I don't know how easy it would be in your application, but a few years ago I added an MSD cam sensor to a Zetec I4 by drilling into a spot on the cam, adding a magnet, and drilling through the head to add the sensor. Something similar could be don ein a cam in block engine, using the timing gear, or maybe even in a similar way that the GM genIII 60 degree V6 is, where the front of the block is drilled, and pointed straight down at the cam.