This is the general type of shotgun that you should be looking for, in my opinion. It has a crossbolt, sideclips, and a mechanical release forend fastener. However, if I were you, I would look for one in better condition than this one. I guess it all hinges on what you want to do with it and what your expections of quality in the finished product are going to be. This one has no cheek piece, if that means anything to you, but the main complaint is that it has pitting on it and the stock will have to be replaced,(it is broken and has been poorly repaired).
Ask yourself these questions, Can it be fixed up into the kind of gun that I would be proud of? Do I have the ability to replace the stock myself? Am I willing to spend a minimum of $500.00 to have someone else build a new stock for it, if I can't?
If it is loose to the point of needing to have the hingepin replaced, then you are looking at a few more hundred dollars to have the gun rejointed. Converting any shotgun to a double rifle take enormous amounts of work and lots of dollars worth of parts besides the original donor gun. Make sure you have a worthy donor gun BEFORE you start cutting it off!
If I were you ,I would keep looking till I found a better quality and condition gun. It will cost you more in the beginning, but you will save many dollars later by spending a few more now.
This is always a good rule of thumb. Bob H.