1993 WR 500 upgrade/modification question

Hey everyone, new to the forum, wanted to take a minute to say hi. Jumping right in with a question though. I've got a 1993 Yamaha Waverunner 500. The thing is, I absolutely love the body style/shape and this particular ski is in excellent shape body wise and right now engine wise. It was a blast to ride when I was a younger kid, but now that I'm older I'd like it to go faster. I haven't really found any upgrades that do much. I don't know if any of you bother working on these older Yamahas anymore but I'm wondering what other Yamaha engines could go in it. Now I know for a fact that LXs were the identical body and had a 650cc, so I'm sure one of those would fit in. VXRs were close to the same body with a 701cc, could I get that to work? What would I be talking about in the electrical department? Theoretically, would I be better off stroking the 500? Is it possible to? If anyone has any advice, please let me know, and thanks for letting me be a part of the site, this seems like a great forum.
Thanks,
Collin