with these you dont use a timing gun at all!set the cam and crank to tdc, then pop dizzy cap off. look carefully at the outer riung of the dizzy housing and you'll find a faint notch, there is a cutout in the plastic dust cover for this to show thru. line the rotor arm to the notch, and thats all there is to it!
thats the bit mate, the rotor has a centreline that aligns with a small cut line on the metal rim of the lower dizzy body when no1 cyl is at top dead centre on the compression stroke.