On the 65-66 389 engines, all the blocks were the same. The HP difference came, as you noted, with the use of different heads and camshafts. All the blocks have the same casting #'s and are interchangeable. The only difference is the stamping of 'YS', 'YR', 'WS' or whatever.
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LEAD, FOLLOW, OR GET THE HE!! OUT OF THE WAY!!!
HONEST JERRY'S SPEED AND EQUIPMENT
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