There were some oddball engines in 53- - - -a hydraulic lifter 235 with a short pushrod cover and a cylinder head that will fit the later model 235's, for instance. Pull the valve cover and count the number of cylinder head bolts, but pulling the cylinder head and measuring the bore and stroke is the only way to be sure which engine you've got. A 216 has a 3 1/2" bore and a 3 3/4" stroke, while a 235 has a 3 9/16" bore and a 3 15/16" stroke. The 235 block is also about 1/8" taller than the 216 from the oil pan rail to the top of the block.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!