How much hp 350 10.5.1 pistons 64cc heads bored 40?

It is difficult to accurately predict the horsepower output of a 350 engine with 10.5.1 pistons, 64cc heads, and a 40 over bore without knowing more specific details about the engine build and setup. However, here is a general estimate of the potential horsepower range:

Stock 350 with 10.5.1 pistons, 64cc heads, and a 40 over bore: Approximately 350-380 horsepower.

With mild performance modifications such as a camshaft upgrade, intake manifold, headers, and carburetor: Approximately 400-430 horsepower.

With more aggressive performance modifications such as ported heads, a better camshaft, headers, and a performance carburetor: Approximately 450-480 horsepower.

With extensive modifications such as a stroker kit, ported heads, a large camshaft, headers, and a performance carburetor: Approximately 500-530 horsepower.

It's important to note that these are just rough estimates and the actual horsepower output of your engine will depend on a variety of factors such as the quality of the parts used, the tuning of the engine, and the specific components used in the build. A dyno test would be necessary to determine the exact horsepower output of your engine.