Tough call really. What's the body condition like? While 3B's are ample with a turbo, a 13B-T is nicer. Trick is, there are next to ZERO 13BT engines coming in now. Back when I was importing, it was pretty easy to pull in a few at a time, but the insurance regs on these has changed. Now the importers have two options: Entire container, or in a working truck.
If you look in the classifieds, or even on clist lately, you'll notice gobs of full JDM trucks coming in now. There have been several BJ7x trucks with 13B-T's AND removable tops lately. As much as I love the 40, those 70's are really much nicer as a daily driver.
For example: http://forum.ih8mud.com/bj70-hzj73-h...rged-bj73.html
But that's not a 13BT, still nice tho.
If you decide to rebuild, you can have the full kit out of Australia for a tick over a grand. Factor in labor, full head rebuild, and maybe a new head, and your $4-5k price is probably about there for a turn-key. You could probably buy a rebuilt one from Crushers up in Canada and have it shipped down for less than that, and then wind up with yours for parts.