I think it may vary by specific manual transmission used by Ford over the years. We looked a new 2009 2-WD 4-Cyl 5-Spd and it was towable. There was a Speed and/or Time/Distance limit but it wasn't prohibitive. We weren't interested in 4-WD and ended up with a Nissan Frontier, 2-WD 4-Cyl 5-Spd. Towable in Neutral but idle the engine in Neutral every 300 miles. The 4-WD version of the Frontier does not have Neutral in the Transfer Case. With manual transmission, it can be towed with the TC in 2-WD High and Trans in Neutral. Basically same as the 2-WD.
I like Rangers, but the seats are uncomfortable and the ride is harsh. The one I drove was the bottom of the line but it felt "eager to please." The Frontier is much gentler, but bigger, heavier, with a much larger turning circle.