I finally installed my 60cc kit a couple days ago and it seems great. I've only ridden it a little over 10 miles since installing and havent had any trouble yet. I wish I could say how fast it will go but I havent tested. I am currently running a Simonini exhaust on this one and may switch the MLM sidebleed exhaust off the other one to test once I break the kit in.
If you do decide to do the kit make sure you upjet. Since you seized sounds like you may need to anyway. Or just make sure youre running oil.. lol.
Check the wiki out for help upjetting if you need it, its simple. I would recommend the kit as it is super simple to install and comes with everything you need to do it. Got it delivered quickly as well.
As someone mentioned before the gearing is an issue for top speed but if you are content with running in the mid 30s the kits the way to go for sure. It blasts and is rediculously powerful for an FA50. I do plan on posting the performance results of my trials once I decide to push it a bit more. Figure Ill ride a hundred miles or so to hopefully break it in as well as making sure I'm not running lean.
Good luck to ya bro, if you need any help let me know.