What transmission?

I bought a used 92 chevy silverado pickup it has a 305 v8. I am wondering which size transmission it has I was told a 3 speed turbo, but then again I was told it had a 350 which it doesnt. The transmission's oil pan is kinda odd shaped not straight rectangular. The only markings on it say "hydra matic DIV of GMC" and a small plate on the side with "196" stamped into it. The gear selector in the cab features Overdrive which leads me to wonder if it actualy has a 3 speed tranny at all. Im just wondering if its a 4 speed or not.