OK I slept on it and realized at least two disadvantages to putting a simple vacuum switch off the 'F' connector:
1) It will not disengage lockup in 4th when coasting - thus engine braking like with a manual transmission.
2) 2nd and 3rd will also be locked under light or maybe medium acceleration. That might be hard on the transmission over time? Also it might be a bit noticeable in overall performance with a low powered V6.
Sooooo I think I'll stick with one of the popular 'kits' as outlined in the link above.
There are two basic 'types' of kits as to installation/components:
1) Internal kits - internal components like the TCC solenoid are replaced after dropping the pan...
2) External kits - purely works with external connectors/sensors on the 700R4.
Costs seem comparable. I don't mind dropping the pan - I drop it every couple/few years anyway to change fluid/filter. QUESTION: In the end which approach is better? What are the trade-offs between the internal vs external kit approaches to locking 700R4's TCC in 4th gear?