Hy oldiron57, according to my parts book, all the main caps listed are the same for 348 and 409, but there is no rear main cap listed in my book, rear main caps are listed for all the others but not for the 348/409. As far as crankshafts go, they are not the same stroke, the 348 has a stroke of 3.250, and the 409 has a stroke of 3.50, hope that helps
