My 1939 edition of United Service Motors catalog 501 for Delco shock absorbers shows the following info regarding 1931-1932 Delco shocks. The part number stamped on the shock cover indicates the following for 1931-32 Chevrolet: 1588C front right, 1588D front left, 1588E rear right, and 1588F, rear left. (List price for the complete shock assembly is $ 3.45) Assuming that your shock has the original cover, 1588D you have a 1931-32 Chevrolet front left. There is a footnote in the catalog stating that "when ordering complete shock absorbers, Valves or valve springs specify valve codes as stamped on absorber, and give make, year and model of car." When I rebuilt the shocks on my 31 Phaeton, I made sure each shock had the correct number on the cover plate, just in case some judge would catch this detail. (Never had my Phaeton judged anyways. The kids, grandkids and myself enjoy driving it and working on it too much to keep it a 'trailerqueen'). Don't know about your non-matching arm. Jo Storaker VCCA 18184