The first CJ was I believe 1955-56. Had the F head 4 back than. Around '66 -67 they but the Dauntless (Buick) V-6 in them as an option. Those V-6 rigs are awesome if you can find them.Much easier to work on yourself, light, shorter wheelbase, parts easy to find at good prices.The newer 4.0 rigs are great also. The mileage you mentioned on the diesel has just barely broke it in. Twice as much is no big deal. The Toyota pickup/Fourunner is another choice for a pickup man. The 'Runner had SFA till '85 if I remember right the truck I believe changed a year earlier.