Consulted my old sales brochures tonite. It appears 76 was the last year the 304 was a part of the Renegade package. From 77 on, the Renegade option is listed as an appearance package, with no performance features. It also appears that 78 was the last year the tailgate/side mounted spare was standard with the solid back being optional. In 79, the solid back was standard, with the tailgate/sidemounted spare being the option.
To answer your question, in all liklihood the Jeep is probably an original Renegade, but without seeing pictures of it, can't say positiviely. I know some dealers back then would put on aftermarket Renegade striping that was similar to the factory but just a little different in appearance and you can tell if the Renegade striping is factory or not by the appearance.