Big block 383 build!

On painting the block, not trying to stir anyone up but for a long time that was common pratice. We used Glyptal paint.
Glyptal is a paint that GE use to paint electrical motors inside. It does adhere strongly to castiron.
Volvo have used it inside their marine motors for ages.
The idea was to seal the new block so no impurites from that casting could come loose and mix with the oil as well as aiding in oil drain back.
It was a big deal in the 70's to paint the inside, I had a ton of motors that I painted, if it made a difference or not, who knows. If you are looking for Glyptal check out electrical motor rebuilding outfits.