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? 

1979 and up got a different size for the fittings.

Makes sense to me, thanks for the info!

I had the same problem on my Atk engine. Mine came with the one you got. I ended up making a coupler myself that would fit. I would have to go out and see how I did it to remember what exactly I did. That was four years ago. My fix worked. These two engines are early EA-71's too. Think they are before 79.