His truck should came with a W56 from the factory, and if it hasn't been changed, it should still be a W56.
As for pricing, a good used high mileage W56 core is worth about $150 - $200. So I would offer him $200 and see what he says. In my opinion, a low mileage W56 will work just like a high mileage W56, so that is not much of a selling point for me.
My 3RZ is sitting in front of some used wrecking yard W56 with unknown miles, and it's holding up to the power like a charm.
One more thing, what year is your truck? For his transmission to be 100% compatiable with your truck, you must have a 1985 - 1988 pickup or '85-89 4Runner. If you have a 89-95, then the shifter bases will need to be changed, which really isnt a big deal, but I just thought I would throw this out for ya
BigMike
