Update on the airbox story....
After much dialog back and forth between myself and the eBay vendor who shipped to me 1974/1975 airbox set...a pair of boxes, in lieu of the 1979 airbox pair set the ad stated and the included mix of photos of 1979 and 1975 airboxes. It was sold as a set, a pair of boxes. I explained in detailed the problem. Now the vendor is trying to get me to agree to one box instead of a Left and Right side mated pair, as though, he he dosen't understand English well? Or so it seems. I'm starting believe that the vendor is being tricky. The sale was sold as a complete set, and now I've discovered that the set the vendor shipped is missing a very difficult to locate component, the left side box has an insert, around which the crossover joint must slip over, apparently it is a pressure fitting. I can't find any information about the component. In the photos, the vendor positioned the boxes as though the part were present, yet upon, again, very closely zoomed scrutiny, one can see light passing through where the component should be and blocking light!
I had hoped that someone here might be able to answer the question regarding different date version cover interchangeability Well, FYI, they very likely are not interchangeable...eg., don't fit. The reason being, the 1974/1975 version boxes have a screw fastener one side and a stamped out, 0.5"/12,7mm long, bent up, at 90º flat tab which passes through a simple slit in the cover, whereas the 1978, 1979, etc, version airboxes also employ a screw fastener on one side, and a tab on the other side. But this tab is a seperate peice of metal, again appx 0.5"/12,7mm long, formed in a 'u' shape and is spot welded to the airbox, appx 1/2"/12,7mm down the side of the airbox. The 1975 and the 1979 tab positions are in different places, it'll either be too tight or too loose, depending on version mix. They gotta go back. I offered the vendor, to swap the two different sets, and I'd even pay half the shipping, presuming that it was honest mistake on both our parts.
I should have paid attention to the reviews, about 5% negatives, mainly not properly representing or sending wrong items..?
Someone welcomed me in the madhouse, now I understand the statement!!
From left - first 4 photos of the tab cover attachment point for a 1974/1975 airbox, and the 5th is for a 1979 cover attachment tab, located in a significantly different position from the box edge: