I towed a U Haul 5X8 trailer cross country from Florida to Colorado a few years ago with my 83 300D and it performed well. Accelerating from a dead stop takes a little longer than usual but when at crusing speed I would just engage the cruise control and she would maintain it on all but the steepest grades. She still got 19-20 mpg towing about 2500lbs.

I recommend you service the transmission more often than the 30 mile "standard" if you do a lot of towing, but other than that and keeping a close eye on the brake system, it is no big deal.
Good luck.

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