1995 Chevy Blazer Engine Cut off

I drive a 1995 mid-size chevy blazer. This truck recently had an engine replacement and needed a tune-up " BADLY". i replaced the spark plugs, wires, and the cap with its inner workings. Once complete the truck ran a lot better. Unfortunately i drove the truck and Kinda "GOt On It" if u know what i mean and the truck Cut off on me. I took a look and assumed that it was having an electrical l problem. I had it looked at by a mechanic and waz told that i needed a crank sensor... Here's my question, did this year model come with a crank sensor and if yes....where is it located exactly?? Keep in mind i replaced the original Chevy engine with a junkyard Brevada Engine.. Thanks!!