FWIW ... The Holy Grail here is the 261 with the "3733950" casting code. This block was designed as an engine for the late AD trucks ('54 and '55 1st Series) and they are a form/fit/function replacement -- requires no modification. You will need parts from your 216 to make it work (depending if you want to keep your 6-volt electrical system). Mine was made in 1959 as a crate motor for the '54/'55 trucks.
Not sure if the early 235's are the same way.
Later 235's and 261s require some mods to work.
Upgrading with the early 261 (if you can find one
) is easy -- your average orangutan with a hammer and an adjustable wrench could do it. Rebuilding it before hand ... um, not so much.
But either way, if you have a choice, go with the 261. Do 26 cubes matter? YES. That's an 11% increase. The difference on my truck (216 to 261) was that I went from a trailer queen (for longer trips, anyway) to a real highway cruiser. If you want to spend time cruising the Interstate or with guys who have done serious power upgrades to their trucks, every cube matters. You don't want to be the guy who the others are waiting for at the tops of hills.
