hard tubes to get me close to the stock pipes then used barb adapters and Good Year teflon lined to bridge the few inch gaps. I left the damper in place and just replaced the FPR.
You can get 3/8 thread to 5/16 barb fittings in brass at any hardware store. 3/8 is a waste unless you do the whole loop since the factory pipes are closer to 5/16.