If you are going to run without the computer, you will need to supply +12V to the lockup clutch whenever you want to cruise. Want to use a switch? A simple toggle switch ought to do the job, as long as you remember to UNLOCK the converter when it's time to slow down.

The connector on your transmission is just a three-wire connector, IIRC. You'll find that it goes into the wiring harness at the firewall, on the passenger side of the harness, behind the valve cover. That will be where you'll want to cut and splice in your circuit.
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I'll edit this thread with more information later, as I have to quit typing and sit down to dinner.

 

From what I am aware of, there are a few different ways the 700 was wired, but this should be the one you need:

700-R4 wiring diagram

In addition to ws6tansam's switch method: It will work fine. However, as a safety precaution, wire the brake light switch to cut power to the TCC. Just in case you have to make an emergency stop and don't have time to flip the switch