I have the 2 crush gaskets, which is all the NAPA (walker) chart shows as needed to replace the Resonator (flanges at both ends of pipe lengths). It appears another gasket is needed at each end, the type with the 2 added holes for the flange bolts. For the 97, is the Walker 31540 Gskt needed or what alternative or are just the crush gaskets sufficient? (approx gskt inner diameter, 52mm)