262, 265, 283, 302, 305, 327, 350 and 400 all used the same basic outside dimensions, height, width and length.

All of them differed internally with different bore diameters and different stroke crankshafts.

The odd size motors are achieved by boring the cylinders larger and using larger pistons or by changing the length of the stroke on the crankshaft or by doing both.

For instance a 350 Chevy which is bored 0.030" larger on the bore, but with a stock crankshaft is a 355. If you add a stroked crankshaft to the motor in addition to boring it, it becomes a 383.

The advantage to the longer stroke is that the motor will make more torque in a lower rpm range than the same motor with a shorter stroke.

I'll give you the formula in case you want to play around with different bore and stroke combinations.
.7854 x bore x bore x stroke x number of cylinders = cubic inches

For example, a 350 Chevy would have a stock bore of 4.000" and a stroke of 3.480", so, .7854 x 4 x 4 x 3.48 x 8 = 349.84 cubic inches, rounded off the 350.

A 350 Chevy bored 0.030" would be .7854 x 4.030 x 4.030 x 3.48 x 8 = 355.11 cubic inches, rounded off to 355.

By boring the 350 0.030" and replacing the 350 crank with one from a 400 small block, it would calculate .7854 x 4.030 x 4.030 x 3.75 x 8 = 382.66 cubic inches, rounded off to 383.

Pretty simple stuff, huh??