Long action stock, detachable mag, pictures and advice please.

Long action stock, detachable mag, pictures and advice please.
I have a Stevens 200 in 30-06 with a center fed mag. I would like to convert a Boyds ross FT thumbhole LA to a detachable mag.
What parts are required?
May I have some pictures please?
I am going to go to my local gun store to see a Savage LA with a detachable mag, to get some ideas.
Once I get the mag conversion done, I would like to swap barrels and calibers, would I then just have to swap mags? Example 25-06 barrel and mag to 30-06 barrel and mag to .308 barrel and mag.
Do they make a .308 mag for a long action?
Many questions,
Thanks and happy holidays,
wcmd.