We have a 305 in a Scout II, a 345 was the larger option, and a 392? would fit if you wanted to install it. The 304 is a great engine, more than enough in such a light "truck", and like a typical scout it gets lighter by the day.
If your engine runs good and has low miles I would re-gasket it to a point, and run it. If it needs major engine work or a rebuild I would look for something cheaper to work on. Although if you want a good engine and don't mind paying for it, by all means rebuild the one you have, it will last a lifetime with good care.
A friend of ours ran a drilling business (soil exploration) and swore by International gas engines. He had one in every truck and piece of equipment he owned, even if he had to install it himself. They are long lasting engines compared to ford or Chevy engines, I have heard something about the different material they used for the blocks....
Grigg