i noticed the cuts were also different on the barrel...
so i cracked open the TM M14 i have and the cuts on its barrel are the same.
so yes there is a specific M14 hop-up cut for the barrel.
EDGI.com makes custom TB barrels.. i highly recommend them for this project.
I have been able to just drop in my TM into this stock.. but i dont find it a great weld.
i would suggest this as a cheap base to build up a nice unique M14.