There are different ARP con rod bolt sets depending upon if the rods are for a steel crank or a cast crank motor.
What is the part number of the ARP rods that you are attempting to use?
Also APR rods have a higher torque specification than the stock rod bolts.
Be sure to use a dial bore gauge to check to roundness of the con rod crank bores with the ARP bolts properly installed and properly torqued. They may need to be resized.
