In a word...
NO.
However, you can use a LOT of things from a Fox on a '90 Town Car. Pretty much everything from the engine, transmission, rear end, and later-model (5-lug) rims (need spacers and longer studs to clear the upper ball joints, though) will work on a Panther car. You can even do a T-5 conversion pretty easily on 'em - the pedals and everything will bolt right in.
It should be noted, however, that if it actually has a 4.6L in it, that is NOT a 1990 model Town Car - they didn't get the 4.6 until 1991, a year before the Crown Vic and Grand Marquis got the 4.6 in 1992. The 1990 is a bastard year because it's the first year of the Aero body style but it still has the old lo-po 5.0 and AOD.
Personally, I'd just keep the thing as-is and drive the snot out of it. A Panther with a 4.6L isn't exactly fast, and you can only do so much to make them a little quicker (dual exhaust, gears, shift kit, 11.25" torque converter, custom chip, pullies, and electric fan), but they're a VERY solid, reliable car. Only sore spots on 'em is that stupid electric blend door actuator on the heater box (I just ripped off the actuator on the '90 I had and opened/closed the heater manually) and those damned power window regulators. Oh, and as long as it isn't yet doing the 3-4 shift shudder, it'd be a good idea to do a total drain on the tranny and TC and then refill with Mercon V.