Dave Cooper,
Hope my 2 answers to your mounting issues were helpful. There are many good stock makers that for a price can provide you with a custom stock for your 54. I'm only aware of two options for a custom stock for the 54 that are already made. The first is here:
http://www.diana-airguns.de/index.php?id=263&L=1&width=800&height=600
If you search through the diana site you will also find an exploded diagram of the 54.
The other is Paul Watts. He made a drop dead gorgeous stock that has an action in it. I don't know if he would sell it but he has one that was made for a former customer that went south. His site is here:
http://www.springgunning.com/
Dave G is also a gifted woodworker (and metal worker) but I'm not aware of any 54 stocks that he's done. You may want to contact him here:
http://davegcustomstocks.com/index.html
Good luck.
kevin