Thanks to all for the info and help!
What I would like to do is go with an oversize rotor from EBC. If I knew what to compare my bolt pattern to, say, for example, that which is found on a DRZ--which, we now know it's not--I would then know which part to order.
On the other hand, it's gonna get kinky, since the rotor pattern will be one thing and the mounting hardware (for WP forks) will be another.
Nevertheless, I guess I could cut through the red tape and call EBC and ask them if they're making an oversized rotor that'll fit my '03 300.
Again, thanks to all for your prompt replies.
TP