NOS Ford valve question

[wrndln]

I recently bought some NOS Ford valves. Some have an indented top with the Ford script on them. Some have a smooth top with a Ford script on them. A couple have no script but look unused. The valve on the left is one I got at a swap meet, has IN on the top and looks new. Could this valve be used only for intake valves? I am wondering if these valves are good enough to use in engines with modern gas and its additives. Any input on these valves would be helpful. BTW, I am building a stock engine, nothing special.
Rusty Nelson