The short answer: In the big wiring bundle coming out of the steering column, connect the "BATT +" terminal on the TTM to the 16 ga. red wire (through a disable switch), and connect the "IGN SW" terminal of the TTM to the 16 ga. dark blue wire.
To document my logic, from Volume 2 of the Service Manual: Page 8W-10-26 shows the ignition switch. By flipping to the pages referenced at the bottom of that page for the six circuits that are energized in the "run" position of the ignition switch, I kind of deduced that the "RUN A21" circuit (on page 8W-10-45) would be the right one. From that page, it eventually feeds the PCM & ECM on page 8W-10-43.
These schematics are much more complicated than I expected, but the good news is mine works fine as hooked up. One note though--I have it connected in parallel with my pyrometer to a pre-turbo thermocouple, and it goes down to within a hair of 200* before it shuts down. I haven't tried the calibration procedure yet to change the shutdown value, but I do often use the over-ride switch if it's under 250* & still running.