Ok I'm tired of the 4 piece POS cork gaskets so I'm gonna rock the FelPro 1piece..BUT...They have a "thick" and "thin" front seal. SO, for an '85 Chevy 3/4 ton 4bolt main, 2-piece rear main seal, which one should I go with..becuase they offer both for the same motor and I don't feel like buyin both when I only need one. I know someone here has done this or has ran into this before. P.S. Engine code "M"