In this episode Buck Strickland rented this car for Hank to entertain a prospective client from Boston, a very touristy type who expected to see all the Texan stereotypes and hallmarks. It is probably an in-joke that this car resembles Boss Hogg's from the Dukes of Hazzard series, although that was set in Georgia.
Boss Hogg had a 1970 Cadillac DeVille, but to me this looks more like a 73 Eldorado because of those things on the front bumper.