hey bud welcome to sailnet. ive got a G30. check out the grampianowners.com site, and be advised if you need parts holland marine out of Canada still stocks Grampian parts...
hollandmarine.com
hope this is a bit of a start for ya, ive got hull number 75.
Grampian Classic 22 Owner
there is the 22 inventory, there will probably not be an HIN persay, but you will probably find a plate under the companionway with two numbers, ie mine is 30 75, meaning 30' LOA hull #=75.
you will hear conflicting stories on these boats... ranging from 'piggish in light winds' (too true for mine...

) to 'they were some of the first fiberglass boats hence they were 'overbuilt' as they didnt know how much glass to lay, so they are tanks and will float forever.' I would def. check it out before i committed. ive got a line on sig. newer cat 22's but, you would probably be spending more money.
oh, the bio on Jim Bisiker and Alex Mcgruer and the history of G marine (and their connection to the O'Day) line is pretty cool and can be found on the Gowners site. Linky here:
HISTORY OF GRAMPIAN MARINE
good luck, if i can help at all let me know.