Brass fittings with pipe threads in aluminum castings shouldn't require any type of sealer. Just don't overtighten them and crack the casting. A long time ago, I used to use a product called "Leak-Lock" which was designed for high pressure refrigeration fittings. It was a thick liquid that resembled blue Loctite. Using sealer on fittings that operate at the pressure of carbureted fuel systems is pretty much redundant.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
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