I had to replace the fuel tank on my 1976 CJ-7. It still had the original 15 gal tank and was rusting badly causing fuel issues. The video covers the basic details, the issues I had and some of the parts.
Youre the first one I've seen that had the same problem as me...The tank that was in my 77 CJ5 was actually, or supposedly, for 1975 and earlier CJs. It's identical to your old one. Mine has the same long filler neck...Cant help but wonder if somewhere, someone got part #s and years mixed up.