I did have an all octagon Penn Hunter barrel on an early Hawken, but I got a very early k-barrel and used it on the Hawken. Then I moved the Penn barrel to a Penn Hunter stock. I found that Penn barrel uses the thin under-rib like on a Cherokee or Seneca.
The other long rifle is a GrayHawk on NewEnglander wood.
I had a WhiteMountian 50 and a 54 NewEnglander that both had cobbed up barrels at the muzzle end. I had to amputate. They both use Contender front sights. The WM is still as accurate as ever. Haven't fired the NE yet.