How can you check deck height on a bare block.?

I bought a RB a while back. Looking at it it didn't appear to have been touched. When I got it home I checked the bores and they were fine so went about prepping the block for machining. It was line honed last week and now its on the fixture to be decked and we've discovered the decks to be about .010 below stock. From previous posts it seems that over stock is quite common but under isn't. The block is still usable - will have to use a .051 Felpro gasket and will end up with .035 quench instead of .039 and CR will be a tad higher. Just wondering if there was a way I could have checked it before I bought it.

yes most are above specs. If you have some dial calipers of that range (10.725 iirc)use a something like a 5/16" trans round roller bearing on the main bore between the bore and the caliper then subtract 5/16" from your reading. Have a helper hold it. You can do a bit of combustion chamber polishing/grinding to get your static CR back dead on if you desire. I'd be more concerned w the .035" quench (rock the piston & check it several times) as that's on the low end depending on how wild the eng will be treated/correct springs.

It isn't very easy to do with a shortblock. With a bare block you can use a long set of calipers but not a lot of people have 12 inch calipers.