I take it the rest of the engine is timed up correct?, the arrows on the cam pulleys face each other, exhaust at 3 o'clock and inlet at 9 o'clock or there abouts, then the little lug on the crank pulley (just left of the grooves on the pulley) needs to be inline with the little tab on the face plate, if you've done this then one of the other lugs on the pulley will be dirctly inline with the crank sensor at the bottom of the engine. Take the dizzy cap off when the engine is at tdc and pull the rotar arm off, you will see that on the edge lip of the distributor itself there is a tiny line cut into the lip and at tdc the rotar arm has to be inline with this groove so place the arm back on and twist the dizzy until there inline and then do the bolt up to hold the dizzy in place, that should be it.