[William]

Depends on the application and how complete it is. Original ZL2 air cleaners had a flat bottom until approximately Sep '69; all used the same flange & seal.

For some time GMPD service air cleaners were furnished with a chrome lid; was never used in production. The later service flange was clipped for some reason.

SS350/manual trans - has the tall extension for the flange/seal assy.
SS350/auto trans - same as above but has the vacuum valve in the snout for the CCS.
396/427 all - no extension. Serviced for many years by GM; was the later unit with the stamped bead in the bottom. Later reproduced. Common and still available.
302 Z/28 - same as BB but used a short extension to raise the flange/seal assy.

'70 Chevelle SS used the same as Camaro. '71 - '72 Chevelles are somewhat different I believe.

Of these the true SS350 units are hardest to locate.