Direct fit with no modifications would be a 54 or early 55 235 or 261. A 216 will also bolt in, with a considerable amount of power loss. Late 55 and newer 235s have a lower water pump position which makes the fan sit too low on the radiator and hit the lower radiator hose. Late model engines can be modified with a water pump relocating plate that allows the 216/early 235 water pump to be installed on them. Some later engines also need the front motor mount relocated.
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!