It's possible to modernize the 216 and still keep it looking original, but either rebuilding the spray-oiler engine or modernizing the internals can get pretty expensive. Going with a slightly newer engine such as a 1954-62 235 is probably the simplest upgrade, as long as you don't mind losing the "original" look of the 216 engine. I'm currently working on a couple of projects that look like an original 216, but have either 235 or 258 cubic inches and a crankshaft that lubes the connecting rods internally, has a bigger oil pump, a hotter camshaft, and a leakproof rear main bearing seal. About the only thing "original" on those engines is the block and the cylinder head.
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!