Port stuffers

In my limited experience with magic glues, all "high-temp" epoxies used in intake manifolds will eventually break loose, and have destroyed engines when epoxy chunks went thru the valves and cylinders. Consider the conditions: temp changing from 0-240 degrees, wet gasoline atmosphere, vibration, etc. If you must, I advise using either a brand-new intake that has never had gasoline run thru it, or a used one that has been sand-blasted, Extrude-honed or professionally chemically cleaned with the most violent chemicals possible, to produce a really clean surface that gives the glue the best possible chance to hang on. Surface prep will be as important as what brand you use. Possibly, an aluminum- filled epoxy so the heat-expansion rate is similar, would work best. I would also call the mfgrs of a couple of the best and tell them what you're about to do with their product, and ask what they think. Personally, I'd drill thru the bottom of the intake runners and use Lock-tighted or safety-wired 1/4-20 screws to hold the stuffers in place.