Sure u can. But if u have a source mod, it might be difficult. rA and hE to many different. But you can ask someone that can help u with this.
If u dont have any source mod, well that is easy, just modified your SQL table.
I've talked with quite a few clients about this... What I normally find is that sometimes when they say eAmod they actually are using rAmod. If that isn't the case they use eAthena for stability or familiarity. Also sometimes it's just a lack of understanding. They search for an emulator and end up finding eAmod/eAthena first and perhaps don't understand that most eAthena scripts run fine on rAthena. Convenience is also another factor where as rAthena aims for 1:1 with retail Ragnarok Online eAmod is more of a custom ready server, so most little things that you see in a private server are already done. But the biggest thing I've found people using eAmod for is the custom battleground system. If you want my opinion rAthena is better and free. Although you'll have to do more work to get things setup. In the end you'll understand more, and have better support.