There will need to be some minor modifications, such as adapting the 216-style water pump to the 235 engine. Otherwise, the fan sits too low for good airflow through the radiator, or there might be fan-clearance problems. One of the advertisers on this site sells a kit that allows the 216 pump to bolt onto the 235 with only minor mods, drilling and tapping a couple of bolt holes. There are some flywheel/clutch/bellhousing issues, I believe, but they're not terribly difficult to deal with, just a matter of finding and bolting on the right year parts. I'm sure somebody will be along shortly with details on that!
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!