Yeah, he's based off of Zoro, but Zolo was probably a pronunciation move made on the side of the translators. Not necessarily a good one, because the reference was made even more obscure by that, and it could have easily been prevented by simply having his name as Zoro and having people pronounce it the way it is supposed to be, since Zolo is far too much on the "l" side (Zoro still sounds more like Zorro than "Zolo").
Regardless, the name persists in the manga, and I'm too accustomed to it to change it now. The reason I don't give it any thought is because I only read the manga (though I resort to the anime when I can't find particular volumes), do it never really comes to mind.
Actually, I was pretty darn sure he is called 'zoro' in the manga. Maybe the translators of the first few volumes translated it as zolo? Don't really know because I started reading the manga only after the fishman island arc and it has always been 'zoro' for me both in the anime and in the manga.
Currently, in Viz's American translation, it's still Zolo. I did watch the 4Kids anime prior to it, but it hardly had any bearing on my saying Zolo. I liked the show back then, but I didn't start to really like it until I started reading the Skypiea arc (though currently Water Seven is my favorite). This is as of the fifth volume of the New World Publications (Chapter 646 being the last and latest volume released).
I don't think it matters much, though. It's merely something that I'm accustomed to, and I will concede that Zoro is the more appropriate name. I probably won't be able to switch, though the airing of One Piece on the new Toonami may change that.
I think the change from Rufi to Luffy is acceptable. In that case, it's meant to be pronounced as something to close Luffy, while in Zolo's he is meant to sound like Zoro with a soft r, as a throwback to Zorro.
The wiki cites that Zoro was named Zolo not as a pronunciation move (well, it may have been), but because of copyright issues with none other than the person he was meant to be an homage to, Zorro.
Though, Derozio, you should be fine. The first few volumes apparently have Zolo as Zoro, and they...for some reason...started to use 4Kids names more and more(though don't quote me on this).