GO WITH MSD....THEY ARE BETTER BUT GET THE WIRES, COILS, IGNITION BOX AND EVERYTHING YOU NEED, AND GET A REPROGRAMMER TO SHUT THE REV LIMITER OFF WITH AND GET A MSD 6AL BOX AND IT HAS QUICK CHANGE REV CHIPS ON THE SIDE.....WORKS GREAT, ALL NEW GM MOTORS ARE COIL ON PLUG IGNITION