Manual for my 2001 said towing with manual transmission was limited to 200 miles, 55 mph. For many towing guides, that is effectively "no restrictions."
My usual tow was 15 to 35 miles at 35 to 60 mph, dictated by roads and traffic. My "over 55" run was about 8 miles each way, most of the longer trip is under 45.
I bought it in 2006, PO had also towed it, probably longer distances at higher speeds, since he was in western Oklahoma. At 30,000 miles I had the oil in the transmission (OEM was Mercon) checked. It showed some burning, so I had it replaced. Dealer flushed and filled with a synthetic gear oil, said they no longer service the M5OD with Mercon, and the synthetic will likely not have to be replaced.
So if you buy one for towing, and plan to tow it fast and/or far between running, flush and fill with the new spec lubricant might be worth while.
If you are looking for something for drag racing, the manual transmission Ranger is not it. Even if you could find the SOHC 4.0 V-6 with a manual (unlikely) the gearing is all wrong for acceleration. Ratios are a lot closer on the automatic, partcularly 5 and 6 speed Ford automatics.
PS it towed pretty well, even on hilly roads with 15mph curves, but when I replaced it with a 800 pound lighter Fit, that towed even better.
Tom Test
Itasca Spirit 29B