88 thunderbird overheating problems

A friend at my work has a 88 thunderbird 5.0 with over 200000miles. He needed a shifter cable for the in floor shifter. Which he claim could not find it any in the usa. Because they discontinued the cable. So he had someone rig a shifter cable to work. But now the car doesnt go into overdrive and it overheats.because it doesnt shift to overdrive. Any help out there on finding the original part or maybe a fix on this issue.

Have original cable repaired. If he's overheating the motor cause he's in 2nd gear at highway speeds, u will the motor roaring he'd better stop before motor explodes.