The camshafts are cast iron. They drill and tap easily. The cuttings come off as coarse granules, not the spirals you would get with steel, so be prepared to capture them. A strong magnet or grease would probably work; I did mine with the cams out.
+1 on the Clewett products (and support).
BTW, check your ECU documentation so you know where to place the hole. Positioning it relative to TDC and the crank sensor is easy, just remember the crank spins twice per cam rotation. Also be sure to position the cam signal so it does not overlap the missing teeth on the crank sensor.
Here's the scope output from my ECU showing where the cam signal occurs relative to TDC and the crank sensor.
