A dual bearing is a good start, I have a couple of each but I'm not selling any of my engines right now especially briggs 5hp stuff since I got half way good getting em to run. Got my last fiver off a TG&Y tiller and it will need rings at the least since it smokes under a load but otherwise runs like new. Popped off shortly after I put a diaphram in it and pulled the cord a few times. I have a briggs book and will have tools soon so my journey into rebuilding and modifying briggs engines can begin.
To my point, I hear nothing but good things about 125cc and the engines he builds and sells so it sounds like you're on your way.:thumbsup: