Most (maybe all) YFs have a slotted base plate that will fit either the 216 intake manifold with the close-spaced studs, and the wider spacing of the 235 and 261 engines. With a spread of 40+ cubic inches among those engines, there can be a wide difference in calibration of a specific carb. The "one size fits none" principle applies here!
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!