Lots of mods done to that rig.
The serial number will be stamped on the frame in two places. One just below where the battery sits, one near the rear wheel hump, passenger side.
Of course there's no way to tell if the frame is original to the rest of the rig.
Lack of a battery box lid on the cowl puts it about '65 or later.
Under-seat tank limits it to mid-1970 or earlier
Windshield has small glass, making it mid '69 or earlier.
The wiper should have an exterior motor on the windshield, if the low-mount is original.
If the tailgate delete is original, it could be one of the rare predecessors to the Renegade I, the 1969 462 option. I'm not fully up on the details of that option. I suggest you join and post your pics at Early CJ5.net > Forums
The guys there may give you a more definitive answer.