YOU APPARENTLY HAVE 4 POSSIBILITIES MASDA, ISUZU, GM-153 CU IN, OR GM 181 CU IN. SINCE YOU HAVE NO INFO , CHECK FOR CASTING NUMBERS, OR ELECTRICAL COMPONENTS GM ENGINES WILL HAVE GM OR DELCO STAMPED ON THEM. IF YOU DON'T SEE THESE STAMPS, YOU MAY HAVE ONE OF THE OTHER TWO. BUT WITHOUT THE TRUCK'S SERIAL NUMBER IT'S GONNA BE HARD TO GUESS GOOD LUCK