I'd get someone with Microcat to check out part numbers for you. As for the oil filter housing cost; I looked into buying one the other week when the front prop on my 90 gave way and smashed it to oblivion :doh: They are pritty expensive IIRC about £140, only available as a main dealer part.
Try searching around for one second hand, i managed to dig one out of a scrap heap at the back of a garage for a tenner! They are out there....