Well, not sure if these are the same as a Mustang or you can make them work, but you can get those at places such as LMR for a reasonable cost, there is another site called "Classiquecars.com" which mentions 80-88 Thunderbird window seals, maybe check them out as well.
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof, T3/T4, ported E6, 255LPH, Kirban, Stinger Exhaust, MGW shifter, K&N, Gillis valve, BP1.5, PIMPx, Koni's
1964 Ford Galaxie 500XL, 390 6V, Big Solid cam, Headers,3.89's, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 312 4bbl intake, headers, 3 Speed, slow and low