which ex gasket set to get

Won’t be any uncorking the exhaust pipes from exhaust manifolds but if using headers with the Remflex collector gaskets (same material) for the reducers/exhaust only to install extensions for at the track they can be reused “if” you loosen the collector bolts just enough to wiggle the pipes free. The gaskets can stick as I found out but luckily I swapped things without tearing or delaminating them.