What year did they stop making the 4 bolt main 350?

The 4-bolt main 350 small-block Chevrolet engine wasn't consistently used across all production years and applications. There wasn't a single year it was definitively stopped. Instead, its use depended on the specific application (e.g., high-performance models vs. standard production) and the year the application was produced.

While many associate the 4-bolt main with higher-performance versions, even those saw changes over the years. Essentially, the transition was gradual; the 2-bolt main became more common in many applications as manufacturing sought cost savings. You'll find many 350s with 2-bolt mains produced well after some models still used 4-bolt mains.

To know if a *specific* 350 has a 4-bolt main, you'd need to examine the engine block itself.