just the pump motor or the whole sending unit deal? if its the whole shebang then its like fitting a round peg in a square hole... actually thats exactly what it is. yj fuel pump/sending unit is square and mounts in a square hole in the tank. tj fuel pump/sending unit is round. they both mount ver ydifferently as well, yj sender bolts down, tj sender has a collar the screws it down. as well the tj unit is a retunless system so the fuel pressure regulator is right at the sender.
but anything is possible. might be easier to find an aftermarket tank to add the tj pump.