you have a t type in my opinion... the interior colors are way too "grey" for the 84GN. the GN had sandstone cloth inserts and door covers, and a light greyish tan console. the black carpet is correct, but the seats should have the turbo 6 in the back rest right below the head rest. those seats were recovered for sure. the darker grey interior makes me think this was a resto-mod car. the dash says regal... my 2 GN's (84 and 87) had GRAND NATIONAL on the dash plaque.
The rims are t- type rims from 85-87. the 84 GN rims were same but had black paint on them, like the general lee rims.
there were NO GN's to my knowledge ever to have "REGAL" on the rear quarters. Your car was most likely a very well restored t type dressed as a GN like my WH1 was. My first turbo buick was a 13 sec 84 WH1 all black with black bimpers, bezels, and the dark dash, but bench seats and column shift and a hood ornament!!! it looked like a GN, but was def a repainted WH1 that was originally white...
it the painter was good, he had that car stripped down before paint, but if it was a friend of a friend, you might get lucky... Un screw a sill plate 9body by fisher), and see if there is another color in there!
I think you have a really, really nie looking car no matter what it is, and Im sure it is worth whatever you paid, but it is dressed like a GN, but not quite the proper GN for the year...
here are a couple links to the proper rims, interior and badging of a GN...
http://www.tctc.com/~avblefty/images/gn84p2.jpg
http://www.tctc.com/~avblefty/images/gn84p1.jpg
you can also try and get into the hot air registry and see if any pix come up with other members' rides to get an idea of what you have!!!
Nie looking car dude!!!
John