76 Duster....Manifolds to Dual Downpipes

I bought a complete exhaust, manifold back, from a member here......can't remember who, and it really doesn't matter.....

I have a stock manifold set-up on a 318 '76 Duster......He sold me a set of dual conversion downpipes........they look nice....no junk......QUESTION......

Do I need the old style "donut" gaskets for those manifolds?? OR are they supposed to bolt down tight to the flare on the downpipes without a gasket?

Local suppliers say they can't even GET those old donuts.....and I have NO idea......haven't needed any for YEARS..........

WHAT DO WE NEED TO DO ???