I have done a few for the long action and it isn't all that difficult.
Close the mag well up by roughly .225" and remove a little material in front of rear action screw so the "L" clip sits properly. If you want to make it more difficult than that bed the mag in place.
On a short action I would assume the same procedure is needed with the addition of filling the screw holes with real good epoxy and then redrilling to proper spacing.