tkv000, any good GEW length Mauser is OK for a 416 Taylor. I have made several in years past.
Here's some pics of my own. I took the pics before I got the checkering done, but the rifle was about 98% finished when I took these. I didn't use fancy wood, but I love this rifle.

I like the 416 Taylor a lot because I could give my customers more gunsmithing for a given budget.
For example, if the customer had $2,000 to spend and we were making a 416 Rigby, we had to buy expensive brass, and an expensive action before I ever got to work. Most actions usable for the Rigby are either expensive to start with or are expensive before you are finished. Yes you can (and I have) made 404s and 416 Rigby's on GEW. Mausers, ( H. Selby's own 416 Rigby was made by Rigby on a Standard Mauser), but you will end up with a lot of time and effort into converting the action to feed the huge shells.
Now the 416 Taylor....... It's easy and fast to convert. So at the same budget you spend a lot less on your metal and that leaves you more to spend on wood and gunsmithing.

Anyway....my 2 cents worth.
SZ