I'm in the middle of converting my '50 3600 over to a big block v6. It is a more straight forward conversion than any v8. It should give plenty of torque but I don't expect to get 20mpg initially. Personally, I think if you really want that kind of mileage and power, you better start looking at the diesels again. You're best bet with a diesel will probably be the 5.9 (unless you can find a good old 4-71!) as it should be fairly simply addapted and they are available at reasonable prices. One more thing to bare in mind is, how many miles do you expect to put on this truck in a given year? If you're not going to be using it for a daily driver over longer distances, it might not really matter much what kind of fuel economy you get (within reason.) If you go with a gas v-8, I'd use what you've got. Otherwise, you may end up like me with all kinds of engines sitting around waiting on a project!
