After I bought the manifolds I ordered an exhaust system from Accurate Exhaust in Roseburg, Oregon. Their web site is Accurateltd.com. They're kind of pricey but the fit was good. They have the complete exhaust system for 67-74 A-body BB/SB with a diagram showing everything. These manifolds from what I understand were used on 71-74 340s. The Rt. passenger side is 318 size and the down pipe uses a ball-type flange so no gasket needed. The Lt. drivers side is 340 size and uses a gasket for the flat flange. Back then I ordered the head pipes and over-axle tail pipes with turn downs and used my own mufflers. The exhaust shop I took it to didnt want to bend and fabricate the down pipes saying it was too tight in there and I would need a mini-starter (which I bought later anyway) and an oil filter relocation kit. They were full of it, so I ordered the down pipes separately and they fit like a glove, no problems. I couldnt tell if the new manifolds helped much since I went dual exhaust from single at the same time which made a difference. I rebuilt my engine a couple of months ago with 920 273/318 heads and the drivers side manifold developed a bad exhaust leak, but the passenger side was fine. I bought some Remflex header/manifold gaskets and we replaced the cheap Felpros on the drivers side and it sealed up the leak beautifully. You should have no problems with the 360 since should be the same size ports as the 340.
