Every 3.8L Thunderbird that I worked on from that generation had TBI. I never saw one with a carburetor.
This is from Wiki;
To power the new Thunderbird, the 3.8 L Essex V6 and 4.9 L (302 cu in) Windsor 5.0 V8 were carried over from the previous generation with the V8 engine gaining CFI electronic fuel injection in 1983, and the V6 in 1984 for US models, 1985 for Canadian models, (which was in turn replaced by multipoint fuel injection on the V8 in 1986 and the V6 in 1988).
From my experience an electric fuel pump won’t last much more than two years in old fuel (with ethanol) . They rust and seize. Sometimes you can hit the bottom of the fuel tank while cranking the engine to get the pump going but it won’t start tomorrow. After ten years forget it, remove the fuel tank, clean it out and replace the pump and fuel level sensor.
from my experience, ford has used leftover parts in later model years even if they aren t listed in the manuals.
my better half has had 3 cougars with the 3.8 in the last 13 yrs, 1987, 1988, and 1997. they have all been remarkably good cars, except for the power windows which came off their holders.
the only reason we don t still have them has been human error. one got knocked into our yard by a kid red necking in the snow, one I forgot to put antifreeze in and the head gasket went and the last one my lovely wife destroyed. I won t go into the details but it took a lot of effort to kill it and it still drove itself to the scrap yard last fall and could have been fixed.
I paid 1400, 1500 and 1600 for them and got my moneys worth. she wants another one now.
the only major repair was a fuel pump on the last one and she drove it on empty constanly so I don t fault the car.
I changed the oil when needed and never had any engine or trans problems.
I didnt try starting it with 10 years of old gas the people that owned it did, and the tank was bone dry when we got it and filled it with 5 gallons, the car has been towed to my house now im thinking either fuel pump because they tried starting on empty so many times or fuel line is clogged.
you are gonna want to drop the tank and clean it, replace the fuel lines, get a new fuel pump and rebuild the carb. the ethanol in todays gas will eventually destroy them. at leastit has not been run with ethanol gas for ten years, so it will take a while for it to destroy the mentioned parts, but you may as well do it now and save yourself the hassle later