Thanks to Sheriff Buford T. Justice
A recent survey of oil filters for the SHO (all years SHOs take the same Oil Filters) included AC Ultra Guard, Amsoil, Castrol Max Pro Plus, K & N, Mobil 1, Motorcraft and Purolator. The full study is 20 pages and will SHO up in a future issue of www.shoclub.com. In the study premium filters were cut open and filtering media was measured and examined.
Top place - AC Ultra Guard in UPFL 400A ( 1/2 Quart size) or Ultra Guard UPF2 has a synthetic media which filters 98% of +8 micron at a very high flow rate.
Runner up - K&N HP-2009 which seems identical to the Mobil 1 but has 16% more filtering media and a handy 1" hex nut on the end to aid removal.
Honorable mention - Mobil 1 - M1-209 or M1 301 which is the same as K&N on the inside but with a little less filtering media.
These all had expensive synthetic filtering media and a very strong (rupture proof) can. The one quart size has almost twice the filtering media of the 1/2 quart size and gives every evidence of problem free service. Pep Boys carries the AC Ultra Guard which not only cleans best but does so at the highest flow rates. Any of the 3 recommended filters retail for ~ $9-10.
Lewis Clay firstname.lastname@example.org also has the AC Ultra Guard for us at $10 each.
Other filters while half as expensive were noticeably less impressive when examined. Given the unique demands of SHO engines I would stick to any of the three listed above.