answer
YES.
That is the engine coolant drain plug for the engine block. There's 1 on the other side also.
The last year for the 327 in a C10 was 1968.
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A 1968 Ford Galaxie 500 with a 390 engine should use a spark plug such as an E3 brand spark plug. This plug should have a tapered seat with 18mm threads.
370 hp
The Chevrolet 327 plug wire diagram can be obtained from most Chevrolet dealerships. The diagram can also be found in Chevrolet service manuals.
The torque rating for your stock 1968 Camaro 327 cubic inch engine is 235 pounds at 3000 RPMs. The torque rating at 3500 RPMs is 255 pounds.
1968 327 SBC (probably out of a Camaro)
1966 or 1968 327.