You can bet that most 216/235/261 engines were rebuilt at least once (they were often "rebuilt" every 50K miles). As stated above, if the 55 is a 55-1st truck engine, that is the better fit (look at the engine serial number that is pressed into the block, just to the rear of when the distributor goes into the block).
If you have to rebuild an engine, go with the '59 (better head and rocker-arm lubrication set-up).
Tim
