That's the problem-factory A/C cars had a different firewall, normally guys replace the firewall when converting to factory A/C. Plus those later boxes are a different animal than the early As. I've got a '68 A/C box in my stash that I compared to when I was building the car, but wasn't close enough for me to consider. Now this is a finished (well, are they ever??) car, so no firewall replacement or major surgery. Just hoping to find a more compact underdash unit to regain some legroom. I wouldn't even bother, but the wife likes the A/C and it's her car, so... You know the rest of the story!