The TPS setting is done not by a specific voltage setting, but by a percentage of the input voltage, which can vary from one vehicle to the other. For this test you should use a high-impedance voltmeter (digital multimeter, FET VOM or VTVM if you're old enough to know what that is).
I finally got smart and wrote it down in text form, so I can paste it in to posts like this:
For an 87-90 4.0:
Test is done with throttle closed, connectors connected. Insert probes through back of connectors to make readings.
For manual connect + probe to terminal A, and - to B. Take a reading, which should be in vicinity of 5 volts but probably lower. Note the reading well. Now move the positive probe to terminal C. The reading should be 16 percent of the previous reading.
For Automatic, use the square, 4-terminal plug. Connect probe + to terminal A, and - to D. Note reading, which should be in vicinity of 5 volts. Now move probe + to terminal B. This reading should be 82 % of the first.