engine question

i have a 1985 S10 blazer 4x4 and it has a newer model 4.3 engine with throttle body and 2 injectors ,,the problem is i dont know the year of the engine ..this number is stamped on the rear GM2134225 i cant tell
for sure if the last digit is 5 or a S, can any one tell me the year of the engine or mail me a website to find out?? thanks for any help .

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