Identifying the casting will tell you if the block is a "low deck" or "tall deck".
From there, you have several theoretical engine sizes that could be derived from either block.

I'm assuming you have standard BBC architecture (low deck), and as such, the engines could theoretically range from as small as 502 (really 396) to the upper 500's

The only way to tell that I'm aware of is to physically measure bore and stroke and do some math. That said, I beleieve there is some instrumentation that can be used to measure CID, but that's beyond my pay grade.

if they are custom engine #'s are only going to tell you what that block was at the start..454, 502, etc and what application after final assembly, if the block has been decked #'s may be gone

The casting numbers are not on the machined pad on the from of the engine they are cast into the block, those would be VIN and suffix codes, See if there is an 8.2 cast in the side of the block around where the oil adapter is mounted, if so then its a 502, the only way you can tell what cu, in they are is to measure the volume of the cylinder.

Edit, if the head is off you can check bore x stroke = cu in

Casting numbers won't tell you that. The same block could be a 502, 540 or 572. It depends on the bore size and crank stroke.

Definately a tall deck ....I can see the spacer on the top of the deck where the intake manifold sits ....so it's a "tall boy" just not sure if it's a 540 or 572

I would think the 572 pete due to the tall deck.

I'm realizing now what a dumb statement that is, but really not knowing and getting answers I feel a little less dumb.

Rob are there 540 tall decks?......if not, then I narrowed it down.

You can build a tall deck 540, but I'd think it's more likely, if a guy buys a tall deck block, he's going to build a bigger CI engine

Gotcha!