choices choices i think im gonna just get the rc4558 from that site and take it from there, if i'm happy with the tone then i'll just leave it
I'm assuming you've already looked inside the pedal to see if the chip was 4558 or 75558... if not you're wasting your money. Don't rush to get things you may not even need.
The chip you want is the very first one on Mouser's list - the RC4558P. Go ahead and get a few, you're spending enough on shipping for a dozen or so to be more reasonable than one.
Jeff