are the 24 spline diffs the same front and rear?

I'm going to buy an air locker and they want the old one back for a core charge. Having removed both propshafts, I've found the front diff has about 30mm play when the flange is turned but the rear only has about 5mm.. If they are the same I was going to swap the rear diff into the front and send the front one back...

or am I being thick?

no they are the same diff front runs on the back of teeth ,can be swapped and often are ,a diffs a diff when sold ,but if quite worn can whine

So there's nothing to stop me swapping them?

A thought has just occurred - is it usual to expect the same amount of play at the flange on both diffs or do the cvs add to the slack? or is it likely to be wear further down the axle?