I'm building up a 1978 GL Wagon 4WD with probably the last new ATK rebuilt engine and am having trouble attaching the air injection 'spider' assembly. The thread size seems to be wrong on my engine. The spider has M12 flare nuts, but the heads on the engine look to have M14 holes, though they are the same thread pitch. The bubble flare looks to be incorrectly small, too, likely being the holes in the heads are sized for larger tube and flare nut. Is there a bushing in the head that adapts these to work, or is there some sort of generational/engine revision mismatch? If its a mismatch, does someone have a spider assembly that fits the M14 holes?