Scrapyard is your friend man.
Any 89-91 Teg will most likely sport a B18a1 and these are a more common site in yards to my experience anyway.
Also there is a gasket to attach the water neck to the head.
Ask your local auto parts place for a water neck gasket NOT the T-stat housing o-ring! If they get that glazed over look in there eyes at the store ask to see a pic and point it out to em.
P.s. Be careful not to strip/break the bolts to the water neck.GL...