if you're looking to push the timing control to the peak... these (assuming SB)
http://paceperformance.com/i-22333783-msd-ignition-billet-distributor-8534.html
http://paceperformance.com/i-22333262-msd-ignition-adjustable-race-rotor-84211.html
or...lock out a stock unit, or i believe some have opted for a parts store lean burn unit, which come fully locked.
in theory....if your engine's initial timing is over 15 degrees, and the unit throws full cruise advance at your engine, it can spark jump. (without rotor phasing) we have
never seen or heard of this happening. and if it did, youd simply bump down your max timing at cruise a few degrees.
pm me or contact me below if i can help further!