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Chevrolet basically took the same block block & crank and just bored it out:
305 - 3.74 in bore and 3.48 in stroke 350 - 4.00 in bore and 3.48 in stroke
Adding that extra bore made quite a bit of difference in the motor. All parts are interchangeable, but the 350 heads should flow better. Main thing would be valve size, combustion chamber size, and port flow. If the heads are of the same cast, then it probably won't matter.
Ford did the opposite with the windsor motor: 289, 302, and 351 (mild exception on the 351, though). All three have the 4" bore, but ford slowly increased stroke, thus making it each like a stroker of the previous motor.
The 289 had a stroke of 2.87", 302 was stroked to 3", and the 351 was stroked to 3.5". On the 351, the block had a taller deck height to support the longer stroke. Almost all major parts are interchangeable (heads, cam, intake, etc), except the 351 requires a wider intake for the longer deck.
Probably more information than you wanted, but  ~Luke Facebook 1969 Cougar - 11.91 - 380HP 2007 GSXR 750 1999 OZ - SOLD - 15.26 NA - 14.71 on 75 shot
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