Being that a Mustang is somewhat small, i'm sure that the back seat doesn't have that much leg room to begin with. It would kinda be like the back seat of my Duster... if you're older than 14, you probably won't be comfortable in the back.
Even for a kid in the back seat... that TV would be way too close.
As far as dealer installed options goes, there was one other i've seen that just didn't seem feasible. IMS, a buyer could get a 1956 or maybe 57 Dodge Coronet with a dealer installed 16 rpm record player mounted under the dash. I guess it was only used when teenagers would go "park" and the guy could play music to set the mood.