if you fit magnets to the flywheel you just drill a hole in the right spot (ie: TDC ) and press in a magnet as per holden black 6 cyl.
number of magnets required depends on what signal ecu wants ,usually half the no of cyls

pick up disc on the balancer is easier but is more exposed
if you need to adjust sensor position maybe better on the front (some computers want TDC position, some want initial timing )

you could use a dissy for a signal
dazza