Exhaust smell

I get exhaust smell in car with the top up (64 Valiant) trying to track it down. I don't believe there are flange gaskets were the exhaust manifold bolts to pipes. I'm running 1964 exhaust manifolds off of 273 does anyone know what size exhaust flanges I would need? 2 1/4 of 2 1/2 maybe? Better yet do you have a part number that I could use?