So can you lock the torque converter and let the transmission shift itself, or do you have to manually shift the transmission if you lock the torque converter?

I'm thinking about this kit for towing myself. I understand how 4th gets things overly hot when towing, but I'd still like to keep the torque converter locked once things are rolling along. Because gosh does the truck drink gas when towing in 3rd without the torque converted locked up, as it does with the overdrive disengaged in stock configuration.

'97 T-100 SR5
'86 Toyota's, the variety pack (all gone)