KPMI Valve guides for 850 Norton

Kibblewhite valve guides for a 850 Norton. The Andover Norton guides have a shoulder on them which fits against the head so the depth is correct. I have just purchase KPMI guides and there is no shoulder on them and they are also a different length to the guides removed. Could somebody please advise what height these need to be installed to as they have no shoulder on them. Thanks