1978
The 4.3L Chevy V6 is among the strongest of production V6's ever produced, especially in its later versions. It was first produced in 1978 and that design stemmed from the 1955 Chevy Small Block V8.
The Novak Guide to the Chevrolet Small Block V6 Engine
Had Several ofn these cars, during my quest for one of them, I came across a 1994 (this was in 2006) former NYC police car, former NYC taxi, 557,000 miles. With regular maintenance, these were tough cars.