A 48-53 truck bellhousing for the 216 or 235 is a bolt-up swap to both the engine and the SM 420 transmission. There is no need to fabricate any sort of Rube Goldberg adapter. You will learn to hate the 2.73 rear end gear- - - -a 235 doesn't have enough torque to handle that ratio. You'll be "rowing it with the shift lever" between 3rd. and 4th gear on any road that's not as flat as a pool table. Something in the 3.30 to 3.50 range will be a lot more flexible, and a 3.70-something gear would be my first choice with any kind of normal-looking tires.
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!