Meh - $500. If it's still running without smoke and clean then what have you got to loose? Compared to their peers of the day, they actually drove great. The early JB (?) series cars had chronic piston ring and rust problems which pretty much maligned the name from there on. By the time the JE's were released they were actually quite good little cars however the badge was forever trashed as evidenced by this thread.
TBH, if it's still running without smoke and the body isn't full of rust then it'd last a few more years which is what you are wanting from any $500 car at best.