Several Europe Dinghys are located throught the eastern seaboard. The Europe Dinghy came from the Europa Moth and bacame a one-design class. Some have asked if these could race as Classic Moths. The only mod really required is to use a CMBA legal sail. The foils do not have to float to be legal. Sailing in the Nationals will require paint to mark sail position on the spars unless a special exemption is made. The owner will need to make a case to CMBA about the hardship painting would cause.
I am the CMBA class measurer. I would be delighted to send a copy of the rules and discuss the reasoning behind any areas where you have concerns. The rules can also be found on the CMBA Web Page in the section "What Are Classic Moths".
The EUROPE DINGHY has good promise as a CLASSIC MOTH. If the current deck and floatation tanks are substantially built, it may be possible to make a significant weight reduction during the restoration and end up with a hull near the minumum weight. A detailed inspection of the hull will be needed to assess this.
The spars on recent EUROPES are no heavier than the spars we use so they need not be modfied. If your sail is in good shape, a sailmaker familiar with Classic Moths can probably recut the leach and head area to make a legal CMBA sail for less than $100. The luff of your sail is cut to match the unstayed mast of the EUROPE. If you plan to replace the mast with a stayed rig, recutting the sail is probably not economically feasable.
The main performance difference between the stayed and unstayed rigs shows up in light airs. The mast cannot be bent to flatten the luff curvature without closing the leach. For this reason pointing ability in light airs is sacrificed in return for additional power as the wind picks up. Also, the EUROPE has more wet surface than the narrower waterline designs some of us are sailing. Since EUROPE's are one designs, the whole fleet has these characteristics and competition is even. If the rig is not redone except for legalizing the EUROPE sail, You should expect to be most competitive in medium to heavy air.