The main issue is the valve size and location. While they might physically bolt on, the 305 heads typically have smaller valves than the 327 heads. This means you'll likely lose some performance if you put 305 heads on a 327. The combustion chamber volume might also be different, impacting compression ratio.
Furthermore, the exact interchangeability depends on the specific year and model of both the engine block and the cylinder heads. Some minor variations in bolt patterns or accessory locations might exist across different production years.
In short: You *can* probably bolt 305 heads onto a 327, but it's not ideal for performance. You'll likely need to check for compatibility issues and expect a performance decrease compared to using 327 heads. It might be fine for a low-performance build or a temporary fix, but not for optimal power.
