haven't had any of my old Eaton HOs open yet to verify what's inside..
but if above is correct and no gasket is required for clearance issues, this is good stuff!
Permatex® Anaerobic Flange Sealant
make sure to stone both surfaces for high spots, get 'em both nice n flat..
under chassis components like this are vulnerable to ground and road debris impacts..
blunt force on a flange mating surface can distress the metal creating high spots and heave the parts apart creating leaks.. if surfaces aren't stoned or filed flat and smooth, they will continue leaking..
I've done this on hundreds of hydrosat trans component cases and end caps to restore sealing surface..
good luck!