Lois
Glad you've dived into land records.
There are two places where the party enclosing the intack is named, Liber Assed and the Enquest Files. The first will have the intack No if you are lucky, the second will not. THere is a very useful shortcut and that is Brodericks Place-names. However each volume is incredibly expensive and there are seven each runn ing to 100's of pages. The parish chapter will name the intack and give you all the references from Liber Assed and deeds etc. If you have an active Manx Society they might like to get one member with roots in each sheading to sponsor a volume - eventually there would be this amazing archive. It is incredible that the whole thing was not published on the web as its not long come out.