Typically I present the data for JFK/LBJ as a unit because Kennedy was shot and Johnson finished his first term and then one of his own, making eight years. Same with Nixon/Ford, because Nixon resigned and Ford finished Nixon's second term, making eight years.
But when comparing first time office holders, LBJ really should be included. The key difference is that LBJ was elected in his own right in 1964, while Ford was not in 1972. So LBJ should be included, but not Ford in order to compare apples to apples.
Johnson was like Truman in three respects: For serving out a dead president's term, for being elected in his own right, and for deciding against standing for re-election.
So, the updated chart including Old Guns 'n Butter himself (note that Trump thus ranks 7th out of 12 starts in this update):
