Is this block junk?

I better look closer there too. I see what you're looking at.

I agree talk to a machinist. I’d have it thoroughly crack checked. Carefully deburring may be your only option since a sleeve usually requires a ‘step’ of original cylinder at the bottom of the bore to trap the sleeve in place between the step and the head. The 383 piston has a very tall compression height, so there’s plenty of shirt to support the piston even with that chunk missing. Welding with something like Crown Royal filler ( not the booze lol) is also possible. But it’s expensive and risky, probably not worth it. You’d have to find a casting repair guy who really knows what he is doing and even then there’s a risk of ruining the block.

Fix it...

I raced a 427 on dirt with seven sleeves without any issues.

My blown 354 had five sleeves.

Fix it