Ken, Do what I did, use spacers and run the stock covers. All you need is 3/8" https://medicemfg.com/product_view.php?pid=109 Yes, they are expensive, they are billet aluminum. What I did was glue the spacer to the head with RTV. Then use a regular gasket. The spacers provide a much wider contact area for the gasket, so it is easier to seal up. I also use these valve cover clamps, http://almackclamps.com/15101.html
I glued two sets of cork gaskets together, then glued them to stock valve covers. They clear .584 lift/1.6 ratio roller rockers. TA may sell extra thick gaskets too.