746.5 NOBO is where Cottonwood Pass starts about two miles up from the trailhead. Or you can go to 751.4 with slightly over three miles to the trailhead access from the redline.
The national park boundary is 755.1 so you start south of that.
https://thetrek.co/pacific-crest-trail/where-do-you-need-a-bear-canister-on-the-pct/ indicates that the bear canister line is 753.9 NOBO.
For the entire trail and canisters: https://www.halfwayanywhere.com/trails/pacific-crest-trail/pct-bear-canister-requirements/.
About fifteen miles south of 746.5 & access trail you have dropped to about 9,000 feet and multiple campsites and water. 732.0 is flowing water and five tent sites.
717.6 is the Kern River. Water. Tent sites. 7,833 feet of elevation.
703.4 is Kennedy Meadows South with Grumpy Bears and other services and a shuttle running starting at 10:30 until 7:00 pm from about a mile down the access from the trail.
This is about six thousand feet of elevation.
Then an ascent and drop over a pass. 7,900 is the peak at 688.5.
684 is your next water at a good stop. Water and campsites.
671 has water and 667 has campsites at 5852 feet.
You climb to about 7,300 at 661 and then it is downhill to Walker.
653.2 is Walker Pass with bus service. Hitching is also common from this location.
So, about a hundred miles. Mostly downhillish.
As of 2‐1‐21, Inyo NF permits beginning at Kennedy Meadows are Walk Up Permits. Regarding locations that show as “walk up”, i.e. Trail Pass, Cottonwood Pass, Kennedy Meadows, www.recreation.gov states: “Due to COVID‐19, until further notice there are no traditional walk‐up permits. The same allotment of traditional walk‐up permits (40%) will be posted on www.recreation.gov every Monday for the following Monday through Sunday.”
The Black Rock Ranger Station is in the Kennedy Meadows area, 15 miles from Triple Crown Outfitters. It is a seasonal Ranger Station. When open, Black Rock issues permits to cover from Kennedy Meadows (mile 703.4) to
Cottonwood Pass (mile 750.2).