I think westcoast was best known in the PWC performance market in the 80's. They sponsored a rider #5 haul'n' Harry Goetcher as there 550/650 mod rider. I have a lot of old jet-ski racing video with him in it. They made some awesome aftermarket parts. My 550sx had a westcoast "rec" head, full pipe, intake etc....very fast for a 550. I have a WC 44mm intake waiting to go on my 650sx. I don't know of much other than swing arms that they made for ATV's....they might have made AM hubs also..
Don't worry...just run watcha brung...