Can you put 305 heads on a 400 sbc that has been bored 040 over?

Yes, you can install 305 heads on a 400 small block Chevy (SBC) that has been bored 0.040 over, but there are important considerations. The 305 heads have smaller ports and valves, which may limit performance and airflow compared to larger 400 heads. Additionally, you'll need to ensure proper compatibility with the intake manifold and check for any clearance issues, as the compression ratio may also be affected. It's advisable to consult with a knowledgeable mechanic or engine builder before proceeding.