Yes, that would work, but let's say U are trying to trade it to a friends mem card, and your friend wants the car, but he doesn't want your entire save. If U bring your save into MK's, hilight the car that U can't trade. Let's say it's the 911(966)GT3, click change car, at the bottom of the list that opens check the box that says "base only", and then select the Ruf RGT. This changes the name only to the RGT, and will make it tradeable. The other reason for doing this is that if the car is not tradeable, U also can't sell it, so if U put it on a friends card that doesn't have a sharkport, they will be stuck with it.
One word of caution, if U are using an older version of MK's, the color code will change with the name, so copy the color code before U change the name, so U can paste it back in after. The newer versions of MK's will change the color codes with a body change rather than a name change, and so this is not a problem.