Putting this here for historical reference. I received an email from Matt's Music. They confirmed the neck specs from Nash:
Here is the PB neck spec below!
The JB is the same but 1.5 nut.
There are no other options, sorry!
Neck Wood Northwestern Hard Maple
Neck Reinforcement Graphite Rods
Neck Shape Medium “C” (.83-.92 +/-)
Truss Rod Single Adjust at Heel
Fret Size Dunlop 6105
Number of Frets 20
Fingerboard Radius 10
Nut Width: 1.625
Fender comparable would be any vintage style Fender neck. Some of the newer ones are a bit thinner.
Looks like the #26 neck above may be closest.
The numbers are what they are but the actual shape seems more like #7.