Phil, they are jacking you around
Phil,
I've seen enough and repaired enough welded covers, oil pans, and gear cases on CAT truck engines to know it will not last. It will be structurally weaker in the heat effected zone of the weld. And the cooling of the weld with it constricted by being bolted up will just induce stress in the cover. It will crack again. Further, there is not enough clearance between the gearcase and the gears or the idler to allow for additional build up to reinforce it.
Dig in your heels and DO NOT ACCEPT their fix, (unless your truck is for sale now)
I half expect the dealer will file for full gearcase cover time and materials from Dodge and reap the difference in profit. I smell a rat here. If they file their claim with Dodge quickly you may take it to another dealer and see if they can pull up a history based on your serial number. It would not surprise me if it said gearcase replaced.
Good Luck, and don't be afraid to get mad if you have to.
Doug Rees