I did an experiment that shows that you can change from the stock bolts to ARP bolts without changing the roundness or dimension of the big end.
I resized a full set of stock 2 dot rods with the stock bolts torqued to 45 lbs/ft. I then removed the stock bolts and installed the ARP's with oil and torqued them to the same value. The big end roundness and dimensions did not change any detectable amount. All measurements were taken on a Sunnen Rod Gauge (which is accurate to a .0001")
The Buick Motorsports Book says that the stock bolts are a very good quality and that ARP bolt are overkill for the stock rods. I've never seen anyone have a failure with the stock bolts that was related to the bolt itself.