Well, it doesn't have reverse, appears to have a slide carb (has the linkage for it) and has a primerless fuel tank. I believe the old style truck had a primer on the tank.
If i'm not mistaken, i'd say it's a 2.5 sport maxx with the 2 speed conversion. It definetly looks like the 2.5 engine head. But the pic is low qual, so zooming in sucks. But it is a 5 bolt head and looks like the 2.5 shape.