i used ford cortina valves... head size was right...were a bit long so cut that off and turned the stem to fit douglas keepers i left the original valve guides in and my head rebuilder put in brass sleeves...its a proprietary system..that he uses on most cars..
valve stem are quite soft..i used carbide segment buti i,m sure could have cut with HSS cutter
bottom line...just find right head size bush or bore the guide...