Hmm.. They certainly look 'well used', and the lack of bearing's not the best sign. You could take the bulkheads apart and give them a good clean before writing them off completely, as the there aren't any teeth missing by the looks of it, and there might be some hours in them yet (can't really see how rounded the the gears are for the grime mind!!).
Another possibility, depending on how far you want to push the credit card, is getting whole new front and rear ends, with the latest spec bulkheads and BP diffs already in, but you'll also have to get a whole mass of other parts if you go down that route (bumpers, SHD driveshafts/axles etc etc). There's a couple of used bits on ebay at the moment, which look good - http://www.ebay.co.uk/itm/hpi-savage-xl-front-or-rear-gear-box-with-alloy-diff-/300892396085?pt=UK_ToysGames_RadioControlled_JN&hash=item460e959a35 (that seller has got a pair of them at the moment), or new, which come with other bits you'll need to convert into X spec (shock towers and body mounts) - http://www.ebay.co.uk/itm/2-x-savage-xl-flux-complete-diff-pinion-29-9-front-or-rear-shock-tower-/111053020811?pt=UK_ToysGames_RadioControlled_JN&hash=item19db469e8b