im not sure if the y7 distributor is compatible with the d15b, but maybe you can fix the distributor that came with the d15b. If the dizzy is not giving you spark its either the coil or the igniter unit. Dont replace those just test them first, there are how to videos on youtube. But before that I would take the dizzy cap off and file down the metal terminals with a flat file and also the metal contact points on the dizzy rotor.