That mag might have the Slick timing tool slots in the rotor.
Take the rear cover off, the distributor out, and look for a slot in
the rear end of the magnet rotor. Depending on which direction the mag
turns (as seen from the gear end of the mag) you'll use the slot marked
LH or RH. Slick makes a small tool that fits in that slot, and with the
tool up against the laminated core in the direction of rotation, the
points should just be opening. This sets the E-gap, and points gap is
whatever you end up with when the E-gap is set. Points gap should be
equal when either end of the cam block is holding them open; if not,
the block might be unevenly worn. The distributor rotor bearings were
also prone to wear.
You could make a tool from a bit of steel sheet of a thickness
that just fits in the slot without slopping around. Would be around
..062".
Putting the ditributor back on you line up the line on the small
gear with the appropriate line (R or L) with the distributor housing,
after inserting a pin into the L or R slot in the housing and through
the L or R hole in the rotor. The pin is left in place to locate the
mag gear to the engine gear, with the #1 piston at TDC on compression.
DON'T FORGET to take the pin out before turning the crank!
Dan