Did the school bus have a side cover that also covered the spark plugs? If so, it was probably a low-pressure 235, and the side cover bolt spacing will be different than your late model 235. I have several of the intake-mounted filters on hand if you're interested in a swap. PM me.
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!