A rear Supercar oddity up for auction

[L78man]

Okay! Yes, This is my block. I didn't find a post until now. I don't know too much about this block other than what I have described. The block was included with 3 Yenko Cars that I bought from the Holub Collection about 4 years ago, along with a few other blocks. The question is if the water jackets are there full of sand, or is the block completely solid. I had an email with an idea to drill a hole in one of the freeze plugs to find out. That's great, but then I have a hole in my block, and it's never been touched. Anyone have any ideas?
I have no idea what this block is worth!