Building a Dana 60/pinion offset?

Hi Im building a Dana for my 71 Duster, on Dr. Diffs site axle calculator it said to choose a 1 3/16 pinion offset(std mopar) or a centered pinion. Is there any advantage to center pinion in tunnel? With a centered pinion both axles would be same length, which would make it easier to carry spare axle. Any Thoughts? Thanks