You can't run PTW files with Civ3, even if you're playing somebody like Rome that is in both versions.
I don't think that we've entirely ruled out having non-expansion Epics, but there does seem to be broader support for PTW Epics. I don't know yet whether Epic 23 will be for Civ3 or for PTW, for example.
In the mean time, you are welcome to go back and play a shadow game of one of our Civ3 Epics. Even well after the closing date, I'm sure there are players who would be interested in hearing about the details of your game.