Drain the block and manifolds. Poke the drains with a thin wire carefully to make sure there isnít anything blocking them. Plugs back in..
Fill to the brim with AF at the thermostat big hose until it comes out the housing from engine being full. Fill the thinner hose there that goes to the manifold, until it comes out the alpha one drive.

Other things could be done previous to this too, depending how fussy you are.
But if you want to prolong the life of the engine and manifolds...fill it with AF for sure.