Are you talking about switching the complete assembly or just the gears from the one axle into yours? If you are talking about doing a complete axle switch I would suggest against it, but if it's free then I guess maybe I would. You could also wait and search for a D44 or Ford 8.8 to swap into the rear and re-gear the front to match.
Edit: I just re-read your post and didn't realize your front D30 was shot. Yes you can switch the axles out to the other axles as long as both axles you are putting in are geared the same. Meaning if the front is 3.55 the rear needs to be the same.