air cleaners

More than two! I'm assuming from your avatar pic that you're asking about the '63-'64 timeframe. There were five different air cleaners on Slant-6 A-bodies in those years:

• Paper element type, about 9" diameter, sits relatively high. "Small 'n' tall".

• Paper element type, about 11" diameter, sits relatively low. "Large 'n' flat".

• Large 'n' flat with nipple for hose from crankcase breather, used on California cars starting '64

• Oil bath type

• Oil bath type with nipple for hose from crankcase breather, used on California cars starting '64

Most cars got the paper element type air cleaners, with no predictability of small/tall or large/flat (neither type requires or prevents any particular underhood configuration or equipment) except the California '64-'69 cars got the large/flat with fitting. Oil bath air cleaners were special-order items, seldom seen. The factory parts cattledog lists additional paper and oil bath air cleaners for cars equipped with governors—even more rarely seen.

The small/tall and large/flat cleaners are both silenced types. There is no performance benefit to doing so, but if you want to listen to intake hiss and roar, you can use the base and bail from a small/tall and the lid from a large/flat. That's how I got my first-ever traffic ticket: got distracted listening to the roar on the 25-mph hills leading up to my high school, came around a curve, cop with radar gun clocked me at 40. Wrote me a seatbelt ticket because he didn't see a shoulder belt through the backglass. I tried to argue: "Officer, look, I have my belt on; the car is old and only has lap belts". He said "Well, OK, I can write you for 40/25, that's $250 and 2 points, if you'd rather have that than the seatbelt ticket which is $30 and no points." Oh. Never mind.