For many years I have used Permatex No. 2 which is thick, non hardening, oil and gasoline proof they say and comes or came in a tube. I haven't bought any for years so I'm not sure it's still available. I've used it in place of various pipe dopes and tapes. It seems to work well an be permanent. DO NOT use it on potable water applications. There's no reason you couldn't use this in addition to tape. I have.
Be careful about over-tightening the tapered pipe fittings in these delicate castings. They will crack, as in split, from the force of the tapered fitting. Teflon tape greatly reduces the friction as the fitting turns in the casting so you can split the casting well before it seems to be over tight. Be careful.
I also would be reluctant to hang a filter by the MTM fitting off the carb air horn because over time the vibration and road shock can stress the air horn and cause a crack where the fitting goes in. I would suggest plumbing the filter down by the fuel pump where you can support it with some sort of bracket. You'll note that the fuel line that runs behind the thermostat housing is captured in a clip screwed to the housing. That keeps the fuel line itself from vibrating and ruining the carburetor, itself or the fuel pump. It also can serve as a support for the fuel filter you are proposing to mount to the carb. In any case don't leave the clip off. GM didn't spend any money on these things that they didn't have to so I assume it was necessary. The same clip also captured the vacuum line going from the carb to the distributor vacuum advance.
