The 41's (the "10B" series) you refer to do indeed have an open push-pin hole in the receiver.
What is hard to determine from photos is there are pieces of steel welded along each side which makes it impossible to use a standard G3 fire control group as it is now wider than will fit.
Those steel pieces also have a projection into the group area, rather than a "shelf" that provides the same impediment.
Conelrad