engines should be broke in hard. rear ends should be broke in lightly. the best truck my family ever owned was a 85 Suburban with a 350. It was pulling a huge camper all over the country for the 1st 50,000miles on the thruway from the day it pulled off the lot. The think got 17mpg and had more power than any 350 or 5.3l iv ever drove. that thing would roast the tires with ease.
bone stock at the moment