I would take a little time now and buy a ATI dampener that will work with the blower drive and have the motor either rebalanced externally or internally before hurting it messing around with a unbalanced blown pump gas motor
Cheap can be fun when done correctly
Not so much when the car is on fire from a rod exiting the block at 5500 RPM
BTW, a low compression motor, under 8.0 to 1 with low boost, under 7.0 lbs doesn't need the timing retarded, at least the last blown pump gas hemi motor I dyno tested didn't
33 degrees with 7.0 lbs at 7300 RPM made 924 HP on CA pump swill a bunch(2002 or so) of years ago