RSC Head Marking on Bolts
 

Can anyone tell me if these are water pump bolts? I have 4 of them with RSC Head markings and need to confirm what they are from. They're 3/8" and are the same length as the circled dogbone exhaust manifold bolts seen on the left. I was hunting for original manifold bolts when I ran across these. Still need to find more of the original manifold bolts as I'm coming up short here.

Thanks in advance for any info on these head markings.

https://i.ibb.co/LvWnswt/IMG-7443.jpg

Think I've figured out these are the correct RSC marked bolts for long water pumps.

If they are 2 or 2-1/4" long measured from under the head then yes they are originally black phosphate. And for long waterpumps both sb and bb 69-up