Yes, a L67 does swap directly in to a GT. You'll need a GTP flash in order to make it work, but all the connections and mounts are all there. Yes, you can do a top swap from L36 to L67, and that project is discussed at great length numerous times on this forum. So long as you do not do pulley swaps without supporting mods, you'll be just fine. I encourage you to do extensive searching on this forum for that information.

I do apologize for this slow response, but this site has gone just about dead silent a few years ago. I'm the only one that routinely checks in, and even then that routine is occasional. Seeing that you just showed up, I'll make it a point to check in more often. Welcome to what used to be a digital version of Cheers. I hope you enjoy what's left of the site.