It would not be an easy mod. The magazine tube mounting band dovetail on the shorter tube is exactly where the opening in the long tube is. You would have to machine a new dovetail on the underside of the barrel where the mounting band is on the long mag tube.
It might work if you used a Spee-D-Loader to fill the magazine tube instead of loading through the magazine port if you tried to use the existing dovetail, but I think the tube would be wobbly since it wouldn't be supported in its full curcumference by the mounting band. It also might be too easy to bend the free end of the mag tube, since it would have a lot more length unsupported.
Just do what I did. Keep a look out for a good used long tube version. Then you can have two model 60's, or in my case, three.