I have been this route:
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=162514#Post162514
http://www.classicgunstocks.com/Husqvarna_45-70.html

You really need to know what load the gun is regulated for. With out that info, you will spend a long time at the range. If the barrels are lined, walk away. I would never have chosen a Stevens 325 for the conversion. You really want a gun with a greener cross bolt to ensure the lock up.

If I had to do it over again today, I would buy Sabatti double rifle from Cabelas.

Pete