I should have taken that bet Mike-T... L84 X 15 bias belt blackwalls according to the dealer order code guide on the Hamtramck Registry site. You could get them as an option in bias belted or steel belted whitewalls. I have no idea who made them but I'll go out on a limb and take a wild guess and say that it wasn't a Japanese, Chinese, or S. Korean tire company.
My "guess" would be G78x15 or maybe H78x15. I don't remember a "84" aspect tire BV?? and :confused: I remember 78's and 70's back in the day. I googled it and found a site with a bunch of cool Fury if'n anyone's interested. http://www.allpar.com/model/fury.html By golly, BV is correct, that naughty Hamtramck site does list a "L84x15" for the 3 seat wagons with J78x15 being std on the 2 seaters. I bet the "84" is a typo? :confused: http://www.hamtramck-historical.com/images/dealerships/1972PlymouthOrderingInfo/1972_page_86.jpg
I missed the two seaters on there. I looked it it up and there was a L84X15 tire size, some size charts show that the L78x15 as about the same size, it works out to a 235/75R15 or a 225/70R15 size tire.
84 aspect ratios correspond to the old numerical sizes, this might have been designated a 8.50 x 15 or similar previously. I stand to be corrected but this is my recollection.