I'm with the rest of the folks, run what you have until it starts stopping you or breaks. Pump with 4 is not seksy, but who cares?
Of course its up to you. Are you doing this for fun and skills or do you want to become #1?
Guns I have run in 3 gun for fun. FAL para, SKS, revolver, pump with 5 round cap with #6 shot and full power slugs.
Funnest setup ever was an old dude with a Garand who had a small bag filled with his clips. He did not win the stage on time, but everyone tgought he took that stage.

