Having owned a number of FJ40s and FJ60s with the 2F engine over the years, I'd say it's feasible. Not desireable particularly, but feasible. I wouldn't tow over, say 23' (a Safari) in a vintage trailer (less than 4,000 lbs) and a vintage Bambi, Caravel
, or Globetrotter would be the better choices. The 2F isn't a ball of fire by itself, so don't expect to do any long hauling or tackling the Canadian Rockies with that combination. You'll need a good Class III hitch with weight equalization and sway control. It'll be hard on the clutch, but it's do-able.
I'd stay clear of the late model units except for perhaps the Bambi 19 & 16s as the newer ones are all too heavy for the FJ60, and larger ones are all wide bodies.
On edit, I actually found a site that has capacities for the FJ60
, and they quote it as having a tow capacity of 3500 lbs, so that gives you a good cap for what you can look at.