With a very few exceptions (53-54 Corvette for instance) the switch to connecting rods with replaceable bearings, aluminum pistons, and full-pressure connecting rod lubrication happened with the 235 engine in 1954. The ideal engine for your swap would be the 54 or 1st.-series 55 engine because of the placement of the water pump. Later 235 and 261 cubic inch engines need a little tweaking to fit your engine compartment properly. There was a version of the spray-oiler 235 engine that was used from 1941 to 53 in medium duty and larger trucks that's not as suitable for an upgrade, even though it looks almost identical to a 216.
Jerry
