Does it have a vertical accent stripe? If it does, it's a 1990. Howatt started the vertical stripe in 1984, so the next possibility from the serial number you provided is 1990. If it DOES NOT, it could be a 1970 or 1980. If it's a 1970, it will have "sharp" contours, while a 1980 will be more fluid. Kinda hard to explain, but if you could post a pic, I could tell you more accurately.
Howattman