If you're interested in having a period-correct engine in the truck, the only V8 that will pass muster is a 1955 265 engine. Here's the difference that will be noticeable to anyone familiar with vintage Chevy engines. 1955 was the ONLY year a Chevy V8 used a bypass-type oil filter which was mounted on a bracket at the front of the engine. The same filter was used on the stovebolt six engines, with a different mounting bracket. 56 and later engines used a full flow canister filter built into the block back in the driver's side bellhousing area. Those 55 265 blocks are as scarce as an honest car salesman or a professional football player who can read and write. The ones you do find will probably be bored out so thin you can read a newspaper through the cylinder walls, after several rebuilds.

Cylinder heads- - - -I've got a casting number list stashed away somewhere in a file that covers about 40 years worth of small block V8 heads, but the ones you'll probably need to look for will have 58 CC combustion chambers and a single diamond-shaped mark on the front of the head. They'll be called "power Pack" heads, and they came on 4-barrel equipped V8s. The valve cover attaching bolts on pre-1959 heads will have the holes on the spark plug (lower) side of the head spaced about an inch further apart than the ones up by the intake manifold. Pre-59 Power Pack heads are also very scarce items. 2-barrel 55 V8 heads have larger combustion chambers and a flat rectangle on the front of the head, not a diamond shape. Ditto on the valve cover bolt spacing for the 2-barrel heads.

Edit: My mistake- - - -the Power Pack heads didn't come out until 59, on the 4-barrel 283. There were some EXTREMELY scarce high compression heads for the Corvette 265 engines with one or two 4-barrels.

Most people ignore the period-correct engine and just drop in a "crate" 350- - - - -sort of like belly buttons- - - -everybody's got one!

Cylinder head casting numbers:
https://www.enginelabs.com/news/quick-ref-small-block-chevy-cylinder-head-casting-numbers/

55 265 V8 heads:
3836839
3703523
3713358

Jerry


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