Once you come to grips with the fact that original air filters for the MGA are not much more than bug screens, the question becomes where to find a modern paper filter element that will fit into the original housing. In CB-201 I detail a method for fitting K&N air filters with a slight modification to the original housings. K&N's are very good for maximum air flow, but maybe not as good as some other paper elements for fine particle filtration. The K&N filter has a long warrantee but depends on having the filter element cleaned and oiled periodically.

On the question of other options, I have assembled a cross reference list of filter elements that MAY fit this application. I say "may" fit, because I haven't verified each one personally, and there are some dimensional differences. The original MGA air filter housing allows space 5-7/8" diameter and 1-7/8" tall. Additionally there is a vent pipe in the front canister that will interfere with any filter element with wall thickness greater than about 1/2", so filter ID should be (preferably) close to 5".

Lots of people have recommended using a FRAM CA77, pictured here (or equal). This one is 6.06-OD x 4.67-ID x 1.97-Height. That would make it even tighter squeeze inside of the steel screen than the K&N filter (which is 5-7/8" dia), and you still have to cut the inside to clear the vent pipe. Following is a cross reference list for CA77 equivalents.

Beck/Arnley 042-8128 BALDWIN PA678 Crosland B1000-41543 Donaldson P528231 FinnFilter FFA10732 Fleetguard AF843 Fram CA77 GRAVELY 010900 GRAVELY 043954 Hastings AF54 JOHN DEERE AM31400

KOHLER 4708302 KOHLER 235116 KOHLER 235116-S NAPA 2373 (not a good number) NAPA SME 702204 (6" x 4.63" x 1.88") TECUMSEH 32008 TECUMSEH 10059 TEHO 21032 WISCONSIN LO194A WIX 42373

On 09 November 2009, Art Pearse in Ontario, Canada wrote:
"Just bought a FRAM CA77. It fits the outer plate (just, by cramming) but the inner plate has a pipe sticking through it which fouls the filter".

As I expected, the 6.06" OD does not fit inside the original sceeen. That makes all of the above noted numbers suspect for the same reason.

A better fit would be the K&N E-3212, 5-7/8-OD x 4-7/8-ID x 1-13/16-H
Notice this one has narrower wall as well as smaller OD, and it is closer to the original height. This one may need one of the original felt packing rings to make up the correct total height without shaving height of the housing. This appears to be a custom application part with K&N. I have not been able to find cross reference to other manufacturers for this part number, but there must be a specific application for it somewhere.