is it same as head/exhaust? 8mm http://www.justkampers.com/search2?keywords=manifold+stud&location=shop&method=match_all&shop_filter[]=0&sort_by=view_count&filter_by=-1 http://www.justkampers.com/shop/exhaust-manifold-stud-head-to-exhaust-j10560.html#
on with nut and bolt but have a slight air leak so carb off now, want to do it proper to see if i can get it tight. the rear nut is an arse to get to but i've ordered a long nut that i used to have on a lambretta as that will clear manifold and allow me to get a socket on it
As Woody states, I'd try the engineering merchants, they are usually a great source for bits and bobs like this.