rearend gears

So while talking to my Dad about the 904 vs 727 conversations that have been floating around he asked me another question to bring up to the masses of knowledge here at home. He has a 8 3/4 rearend in the Duster with a new Auburn posi unit with 4:10 Yukon gears. They recommend not driving the car hard for the first 500 miles for a break in period. This car is a strip car, how the heck do you break in a rearend for 500 miles in a bracket car?