What size of bell housing do you need to fit a Chevy 305?

A Chevy 305 small-block V8 uses a standard Chevy small-block bellhousing. There's no specific size designation; it's the same bellhousing pattern used on many other small-block Chevy engines (e.g., 283, 327, 350, etc.). You'll need to specify the transmission you're using to ensure you get the *correct* bellhousing for *that* transmission to mate properly with the engine.