Hey everyone i would really appreciate some help with this. What is the difference between the 520 and 620 diff eg axle splines, housing lenghts. Will they both fit straight into a 1200? A wrecker has both, one with the alloy carrier and one cats iron. Which is better, obviosly the alloy one is lighter, but is it harder to get centres to suit? can the alloy carrier be fitted to another centre without dismantling the entire diff? I know thats a lot of questions, but any help at all would be great. Cheers.