Will a Oldsmobile transmission fit 305 Chevy motor?

No, an Oldsmobile transmission will not directly fit a 305 Chevy motor without significant modifications, if at all possible. Oldsmobile and Chevrolet used different bolt patterns for their transmissions and engines, different bellhousings, and often different input shaft diameters. You'd need an adapter plate (which may not exist), and even then, you'd likely face significant challenges aligning the engine and transmission, and potentially dealing with other incompatibility issues. It's not a practical swap.