Chris, your rear PR3 with 8K has about the same amount of tread left as my PR4 with 6K, or just a bit more (.060" to wear bars). My last PR4 went 13,000 miles. This one won't make it that far. I'm not sure I'll buy PR4s again. I looking at Pirelli Angel GTs or Bridgestone T30s now. Your front tire looks better than my front PR4 with 6K on it as well.
I think you would be fine to replace the rear tire without replacing the front. The worst that could happen is if you weren't satisfied you'd have to get a new front too. The only thing I wouldn't do is use one of those belted Shinkos with the PR3 up front even though it might be fine.
I think you would be fine to replace the rear tire without replacing the front. The worst that could happen is if you weren't satisfied you'd have to get a new front too. The only thing I wouldn't do is use one of those belted Shinkos with the PR3 up front even though it might be fine.