A dial caliper will let you measure the distance, divide by 2----------but that really doesn't answer the question-------

there are methods to sleeve about anything-----however lots of things will limit you on size-bolt or cooling holes close to sleeve will crack out and if bolt holes in deck you will probably lose clamping force at that spot-----cooling holes can be filled with plugs and redrilled-in fact , back in the days of 392 on nitro we filled those holes with plugs to reinforce deck, but of course had to resurface decks

Was there any specific type of block that you wanted to do?????