I agree with those that say a dial caliper isn't accurate enough. Even in a best case scenario with a lot of care and skill the best you can hope to determine is deck height at the mid line of the bore. It would still be all but impossible to determine if the deck was tilted ie. not exactly 90* to the crank centerline. Also the main bearing bores should be align bored prior to making any measurements. You can't do that at home so you may as well let the machine shop check the decks while it's there.