The 3756519 block casting was used from '58-'62 and is a 283 cu.in. engine. The date code, if I'm reading it correctly from the first photo ends in a zero, which would date the casting to 1960. Looks like B 1 0, which decodes to February 1st, 1960.
The spread-bore 4bbl intake manifold and valve covers appear to be from a later engine or engines. Heads may be mid-60's based on the casting style and end-marking.
Chevy introduced the spread-bore Quadrajet on the 396 in '65, and also used that on small blocks starting with the 327. I don't believe the spread-bore manifold/carb combination was ever used on 283s from the factory, but not positive on that - possibly in '66 when there was a 4bbl 283.
Good resource here on
SBC casting numbers and stamped engine numbers.
Doug
