I notice that after a couple of heat cycles on a new engeine, the pan bolts tend to loosen and need to be retorqued.

I use regular old Felpro gaskets but applied black silicone to the pan rail of the block and then put my gasket on. Despite all the bolts being loose, I didn't have a single leak. I retorqued for good measure. The valve covers and transmission pan are the same way.

I do make sure all the surfaces are cleaned with brake parts cleaner first. I took great pains with the rear main seal cap and even ran a bead of black silicone on the inside of both edges where it meets the block.

My 505 is the first engine I've built that doesn't leak a drop!