I use good old Aviation Form-a-gasket. Used sparingly, a thin coat works great and seals gaskets & metal-to-metal surfaces. Cheap effective & easy to find.
Used it for years with no issues, but still comes down to proper surface preperation of course.

1956 GMC 370 dump " 'Tater "
1970 VW Volksrod "the Black Bomber"
2007 Chevy Avalanche
2020 Jeep Cherokee Trailhawk,
2005 Harley Davidson FLHTCUI

I dig all cars, old and new, whether they were hammered out of American iron, German steel, or Japanese tin cans. Being unable to appreciate them all is missing out on a world of great things.
But thats just MY opinion! :P