Fumblin '46-
In addition to the 235 and 216 you could find a 261, which was basically the same as a 235 but had a bigger bore cylinder so greater displacement, more torque/HP. The 261 JOBMASTER engine came in school busses and dump trucks, etc... Just like the 235 it'll bolt right in to where your 216 used to sit.
The big advantage to the post 1954 235/261 is the full pressure oiling as opposed to what the pre 1954 216/235 had, 'splash oiling'. Splash oilers, in oversimplified terms, relied on oil splashing around to properly lubricate the engine where full pressure oilers have a pressurized oil galley that circulates oil to all the places it needs to go at roughly 45 psi. That means the 235/261 oiled itself better, didn't heat up as much and didn't ruin critical parts, like bearings, as easily or frequently.
A critical difference between the 235 and 261 is that the later 261 was set up for full pressure oil filtration while the 235 only had bypass filtration. So, while the heavy duty 261 could filter all the oil under 45 psi of pressure the 235 would filter 10%-20% under less pressure, so less filtration.
Use the search feature in this forum to read up on 235s, 261s and read the tech articles on swapping your 216 for a full pressure engine before making up your mind. Many people say there is little HP/Torque difference between the 235 and 261 because a 1954 tech article specs said so. Perhaps that is correct and the potential of the 261 is in buildability and durability with the full pressure oil filtration. The 235 can be converted to full pressure oil filtration by drilling a hole in the block and threading it which leaves only the little differnce of 26 Cubic Inches of displacement, sort of like the difference between a 327 and 350 small block.
