Most people would jump at the chance to have a 292, and make a boat anchor out of their 230. Unless you're trying for a concours restoration to win car shows with, stick with the bigger engine. 230's were also notorious for getting cracks in the block between the valve lifter bores, which sometime let coolant leak into the oil. The motor mounts would have to be modified to install a 292, as the 230's and 250's had the front mounts directly across from each other, and the passenger's side mount is offset toward the front on a 292.
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!