Everyone has their own opinion, but if I were looking for an older classic truck to use as an everyday trailer puller, I would get a Task Force or newer. Much easier to get a V-8 under the hood, and a lot options are more readily available to add some of those other creature comforts.
Just for fun check out entry number 28 in the IRWIPI contest, now that would be the ultimate trailer puller. While you are already there, you may as well vote for it.
John