Looking around, this is obvious. Someone smeared the numbers 441 on the firewall with paint. I'm assuming it is a paint code. My back bed panel also has 441 written on it (with soap?) with a few more characters.
Authentic 1971 Chevy Factory assembly line markings. Very cool/rare!!
My SPID shows my color
scheme as # 551. That's probably because of the White addition.
Moving along... here's the block on the engine stand.
This block comes equiped with two holes (L or R) for a dipstick. One plugged.