Kearsarge Pass to Bishop Pass Guide Book

John Muir Trail Guide by Elizabeth Wenk. It's available in a Kindle edition so you can take it with you. The applicable part is about 14 pages after a quick look.

Does it list all the campsites along that 62 mile stretch?

In appendix C there is an entire list of JMT campsites indexed by trail miles (North or South) and UTM coordinates. I am seeing this as 42 miles from Bishop Pass to Kearsarge Pass.

I wasn't adding the distance out to both trailheads. Without looking that would bump the mileage up to your figure. There are no campsites listed for the route in and out trails. If there is a campsite at the start of the trailhead it is noted in Appendix B "Resupply routes."

Is it feasible to finish this section from Onion Valley TH to South Lake TH in 6 days 5 nights? Having never hiked at these elevations I am not sure what kind of distance per day I should expect to accomplish.

How many miles per day would you usually expect to cover at the altitudes you are used to? If you can comfortably do 15 miles per day at lower elevations but with plenty of up and down, then I would expect you can probably handle the 10 or so per day that you'll have to do on this trip. But you can never tell how easily you acclimatize to altitude until you have tried it. A few tips for helping to acclimatize are to sleep fairly high (like around 8,000 feet or so) the night before you start hiking, and to drink plenty of water – not only once you start hiking but for a couple days before. Plan for your first day to be the shortest and the last day to be the longest – you'll get stronger each day as your body adapts, plus you'll go faster as your pack gets lighter.
Campsites are easy – it's a lot harder to find a spot that isn't a good campsite in that stretch than one that is. But there are some great areas – anyplace near Rae lakes is great if you stay away from the bear boxes and thus most of the people; anywhere fairly close to Pinchot Pass on either side is great unless you don't like to be above timberline – ditto for the Upper Basin and Palisade Lakes. If you like to camp in big trees then there are a bunch of nice spots between the golden staircase and the junction with the trail up the Dusy branch. And Dusy Basin is fabulous, so if you've picked up speed and can afford to have your last day be a little short, then a camp there is very nice.