interesting - GPSies, used by Chris, gives 3,700 feet of climbing for day 3, whereas MapMyRide gives 2200 feet of climbing. MapMyRide gives 2900 feet of climbing for day 4, which might translate in to about 4,900 feet of climbing, but I suspect that the figure will be higher, because, if MMR doesn't pick up the minor ups and downs, then it will underestimate the rollercoastering on the A68. My bet is that Chris will come up with a figure well in excess of 5,000 feet on GPSies.
Whatever the number I suggest that you do not follow Google Maps Streetview from Corbridge to Rochester, because if you do it will make you cry.