Production change from BA10/5 to AX15 occurred ~3/1/1989. Physical ID: BA10/5 main case is two "suitcase" halves that bolt together lengthwise along top & bottom; AX15 main case is solid. Shifter tower is offset toward front of base on AX15 and toward rear of base on AX5. OEM NV shifter base housings are plastic; AX base housings are aluminum.
