Just an update:
JC Whitney doesn't appear to offer the inside window belt online. I was able to find it on Rockauto.com:
PN: 01484X2, ~$25 for 2 4 ft segments + $10 shipping.
They have 1599, the style cracked shows, but it only comes in 3X32" segments, so you'd have to order 2 (at $50/3 segments) to get all the windows. I think JC Whitney still has 1599-4 (Mfr #)/1JA 819752 (JCW #) for $18/4ft segment +$9 shipping. 2 segments should do it if I remember the window width correctly (about 30" in front and no more than 15-20" in the back?). So I think it's cheaper to do rock auto for the inside and JCW for the outside.
As for the window channel, rockauto.com has Fairchild 0452 for ~$15/8ft (04528). Little more than Precision, but at least it's another source in case we loose either one.
You can browse the weatherstripping at rockauto under the tools and universal parts tab.
Hope this helps.