Just for grins, take the fan off and make a highway run. I believe you'll figure out pretty quickly where the noise is coming from. Unless you're running ridiculously low profile tires, the 3.55 rear end you've got already is just about ideal. There's nothing whatsoever wrong with letting a 235, or even a 216 wind up where it's designed to run, as long as the bottom end of the engine and the oil pump is in good condition.
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!