OK I talked this over with my gunsmith and he said he did not see why it would not work. I figure I will ask here too. I got a Remington 742 that the receiver is about half worn or half usable yet. (I am talking about the chatter marks on the rail that these guns get) This gun was just given to me free. Now I know that some folks convert these to a 760 pump using the 760 parts.
I took off the forarm and pumped the action by hand and it worked fine. What I would have to do is disable and plug the gas port and then modify the forarm to fit the action so I could hand pump the gun. I was going to wait until it got bad enough to become a single shot but my gunsmith said if your going to do it do it now to save any more wear on the receiver rails.
Here is a picture copied from Wisners that show the action. As you can see the action is slightly compressed in the picture with the shell holding the bolt partly open. The gas port is the small tube on the right side and that would have to be blocked then the forearm modified and shortened to and fit to that Tube slide assembly that fits over the rod with the spring. Every thing would be left intact except for the gas port being disabled and the forearm fit to the slide assembly. As is the gun probably only has a few hundred shots left give or take. By doing this it should now last as the receiver will not be battered by the pounding of the semi auto action.