IMHO, if you have the time, why waste the bullets which are two different weights and the primers. The powder will of course be an unknown and I would personally dump it.
As far as virgin brass not being as accurate that totally depends on your chamber and how close to minimum spec it is. When I set up a new barrel on a rifle I always try to use a minimum spec reamer. Making sure it is true to the axis of the bore is also a very important issue as is machining a removable pilot that fits the bore perfectly.
If your rifle was accurate with the components you used previously don't change anything other than maybe increasing the OAL by seating out the bullets so they will be a bit closer to the lands to make up for the leades wearing.
If the bullets are the same as you regularly use and you are loading for hunting purposes you may even be able to use them in your reload. As for the weights being different, unless that is all that was available that wasn't a great idea. With only 20 rounds of each you don't have enough to really work out each batch well. More than likely that is why Ganderite suggested you pull down the cartridges to their individual components.
Have you annealed your old cases????? If not, it's very likely they are just fine and with a half hour of effort they would be as soft and good as new.
This is IMHO of course