I have an '05. I tow in TH even as light as my boat because of the 3rd gear TC lockup. Sometimes I wish I had the OD off option when towing the back roads just to keep it from shifting into OD at 45-50mph. OP, if I was in your shoes (no TH) I would run it in OD until I started getting a lot of unlocking and locking of the TC. I would then lock out OD so it would run in 3rd and locked TC. Go back to OD when back up to maintainable speeds.
The death of the 48 trans is heat build up and when the TC is unlocked it will build heat quickly.I have pulled heavy with my '05 since new and have had it tuned for about half of those years and my original unbuilt trans is still doing great. I run my tuner turned all the way up.