Need more info on what you have

Stock heads & stock valve covers, you're stuck with the cork & rubber usually 3/16" a minimum thickness.

or

Aftermarket heads & Cast or Fabricated valve covers, I can help with this as I offer a .050" thick gasket.

If you have Stock heads with Cast or Fabricated valve covers and feel ambitious you can remove the heads and have the valve cover gasket rail machined true & flat so a thinner gasket will seal. In fact this will help ANY gasket seal better for you.

Just some food for thought wish I would have machined mine while they were off. It WILL be done next time.

Greg

Oh forgot about the rubber gaskets. I think Fel Pro or somebody makes an 1/8" rubber gasket but don't know how well they seal