Is it good to put a 305 head you have from 1985 Pontiac on 72 Chevy 350 block?

No, it's generally not a good idea to put a 1985 Pontiac 305 head on a 1972 Chevy 350 block. While both are small-block Chevrolets, there are significant differences that will prevent a direct bolt-on and likely lead to performance issues even if you *could* force it on:

* Bolt Pattern: The head bolt patterns are different. Pontiac and Chevrolet small blocks have different head bolt patterns. You wouldn't be able to bolt the Pontiac head onto the Chevy block without extensive and likely impossible modifications.

* Valve Angle: The valve angles are different. This means the valves won't align properly with the ports in the Chevy block.

* Combustion Chamber Design: The combustion chamber design and shape will differ substantially, leading to incorrect compression ratio and potentially poor performance or even engine damage.

* Intake and Exhaust Manifold incompatibility: The intake and exhaust manifolds designed for a Pontiac 305 head won't work with a Chevy 350 block.

In short, you'd be facing a massive and likely fruitless undertaking. It would be far more practical and cost-effective to find a set of heads specifically designed for a 1972 Chevy 350.