.060" MINIMUM on the block clearance. .080" MAXIMUM Then tear her apart, clean the shyt outta her, put her back together!
Watch the cam lobe clearances too. You'll see what I mean when you put it together. Big Nasty cam lobes hanging down, whilst big nasty crank lobes are pointing UP, could be a problem. Watch the rods here, rod BOLTS down below. Watch the bottom of the pistons at the bottom of the stroke too, they are SOOOOOO close to the crank throws, it's not even funny. Kinda scary actually. When ya put all the big nasty shyt in a small block, it get's REALLY close all the way around. Watch for stupid stuff, things you never thought would hit, ARE GONNA.
Don't be scared. Noones lookin. Stroke it.
We'll help you out along the way bro, just build the darn thing.
If you build it, they will come!