Wouldn't run a 4500kv motor at 3s personally. I would stick with 2S
Now if you want a 2S battery recommendation I do have a RC18b that I use a 2S in, and the battery is pretty cheap(if in stock).
As for the diffs I'd ust replace em if they strip. No real point in going through the work. I used a 4800kv motor on 2S in my HPI recon which has a plastic diff, and the diff didn't strip(rest of the vehicle got totaled though, but the diff was still fine