I'd say that is normal for a typical bracket race type of engine. When you use off the shelf parts you'll have tolerances for stroke, rod length and piston deck height. Add up those three tolerances and you'll get a few thou of variation from top to bottom. This is assuming that your deck is square. If the deck isn't square then you have another tolerance in the mix. I wouldn't worry about it unless you're a class racer. If you're a class racer then you probably should've had the crank indexed and you should've bought 3 or 4 sets of rods so you could pick the 8 that matched.