Learn a lesson on bad gas
I just ran into this problem on a slant 6, here's what I did:
Take rockershaft and rockers off, leave the pushrods where they're supposed to go. Pour about half a quart of marvel mystery oil (or seafoam, I had marvel on-hand so thats what worked for me), across the valves, trying to get the springs and stems soaked with marvel. Drink a beer or 2 and let it soak.
Use a dead-blow rubber mallet and hit the valves a few times until they are moving. You'll hear and feel when the valve moves, it will make a springy, hollow metal sound.
BTW, if you run shite gas after doing this, it will re-stick the valves. The only true way out of this dilemma is to get rid of all the old crappy gas from the fuel system, even if the motor is currently running on it.