I have one of those oil filter conversions on my TR4A that I have used for years. I have been using a FRAM 3600. I just found this oil filter online from K&N. I must say, having a 1" nut welded on the end to remove the filter sells me! Here's the link for the K&N filter that replaces the FRAM... http://www.knfilters.com/search/product.aspx?Prod=HP-2009 --Justin