Welp, better that it happened 130 miles from home and not 1,300 miles. 96k miles on my truck, frequent towing so not babied, aux cooler...but it seems the stock torque converter is no longer up to the task of towing relatively heavy while also being tuned. 130 miles from home, climbing a small grade at 65MPH into a stiff headwind, trans temp 180F, truck downshifted to 4th and a few seconds later started the infamous rumble-strip shudder. Manually downshifted to 3rd and it stopped. Upshifted to 4th and it started again, upshifted to 5th and it continued as long as I was on the throttle. Let off and it stopped. Turned around and "limped" it home. I did feel it start to shudder slightly about 15 minutes prior, same deal. Downshifted to 4th and a few seconds later is started to shudder mildly, such that I thought (hoped) it was just the road coming up and over an overpass hill. Nope. 
So, there's RevMax - 6L50 2.8L Duramax Diesel Billet Triple Disc Torque Converter - Revmax Converters
NextGen? Never heard of them - Xtreme Tow™ 6L50-E Torque Converter (nextgendiesel.com)
Are there any others? It's looking like RevMax is the best option here, but if anyone knows of others then let me know. I'll be pulling the trigger this week so we can hopefully head out next month instead.
So, there's RevMax - 6L50 2.8L Duramax Diesel Billet Triple Disc Torque Converter - Revmax Converters
NextGen? Never heard of them - Xtreme Tow™ 6L50-E Torque Converter (nextgendiesel.com)
Are there any others? It's looking like RevMax is the best option here, but if anyone knows of others then let me know. I'll be pulling the trigger this week so we can hopefully head out next month instead.