As posted earlier... 57 GMC pickups used a 347 cubic inch Pontiac Motor with a 2BBL intake.
The '57 and '58 pontiac and gmc V8 intakes are interchangeable as are the '57 and '58 crankshafts. The '59 gmc '336 motor is based off the '59 pontiac 389. The '59 336 intake is not interchangeable with the '58 336 V8 or the '58 pontiac 370. The stroke changed in the motors between '58 and '59. As the stroke was increased, so was the deck height of the block. Although the heads are interchangeable the intakes aren't as the '59 intakes will be wider than the '57-'58 intakes.
All the Pontiac based GMC V8s from 55-59 are considered "Big Blocks".
John
