What size exhaust pipe? Dakota manifold p/n's?

Hey everyone. Looking for advise. Finally getting my 65 valiant wagon back together. 360 magnum and 904 trans. Using stock 273 manifolds and not crazy about them. Would 2.25" exhaust work better than 2.5" with these manifolds? Also does anyone know what part number Dakota manifolds to look for should I choose that route? Thanks in advance .