This kit has never been mounted but I'm pretty sure I drilled the kit to m7 ( yes on a drill press!!) . I've got rings new at least two sets that come with this as a bonus. This particular ancient kit was the subject of many posts on modding it by a great builder Dan Ott as I recall. Basically if you want to learn high end porting this is the kit to learn magic because it's possible to remove the inner cast iron sleeve , go insane on the surrounding aluminum and then pop the sleeve with its own modifications that can be done from the outside in. Then reinsert. Or I guess just run it as a light mod as it is. This I'll sell for $55 plus shipping. Again it's new and only improved.