A 305 fitted with a 400 crank has 329 CI. (3.736" bore x 3.75" stroke)

You can get pistons for this set up.

Does not rev like the 305 but has more overall power and much better torque.

350 heads are rarely used on 305s. When they are used care must be taken to insure that the intake valves, in particular, do not contact the lip of the cylinder. 305 valves are smaller and closer together. 283 heads are occasionally seen on performance 305s and after market heads are also available.

400 cranks are externally ballanced. Look for a weight on the edge of your flex plate or flywheel. The harmonic ballencer will also be cast with a visable weight but it is hard to see when the engine is assembled.