So it turns out the fuel-safe JB Weld isn't very fuel safe anymore. I don't know if its the ethanol or what, but I was using it to seal two aluminum pickup tubes in my fuel pickup, and it turned it back to an almost rubber-like state. Ended up removing the tubes and drilling it out for bulkhead fittings instead.
Also changed over to a radiator hose filler neck on the intake manifold that has a radiator cap on it, since my radiator is now mounted a good bit lower than the intake, and it would be a nightmare adding coolant and burping the system otherwise. Unfortunately, I think I'll have to redo it, since the radiator hose moved on me and raised the coolant level in the intake, so I'm betting the gasket got saturated before it cured. If it did, I'll rip it off again tonight and just use a fat bead of permatex instant gasket and call it a day.