Good Mausers to build on would be.
Parker Hale M81,82,84,85.
Commercial FN Mausers.
Spanish commercial Mausers.
Kongsberg weapons KV 67.
The Czech Mausers are generally of good quality.
CZ VZ24.
Swedish Mausers.
The Turkish actions are often of good quality,look out for what Sandwarrior mentioned though.
If i was going to do a build i would have chosen a commercial, closed top action, built with modern steel, witch avoids potential problems.
They were generally held to higher tolerances when built.
Comes from the factory drilled for scope bases, with a properly bent bolt handle.
Improved bolt shroud and safety, and the closed action helps make it more rigid.
If you want the very best Mauser receiver available, contact Prechtl in Germany.
The GS04 they use is certainly the most impressive Mauser action built ever.
It's the one is used in the GOL rifles the GSG uses.
Precision machined, whole reciever made from one block of steel.
A beefy Octagon receiver with flat bottom, fora better bedding surface, and closed design to maximize stiffness and rigidity.
One piece bolt with oversized bolt handle.
3 position m 70 type safety.
Intergal ZF/ weaver/ Picatinny rail 20, 30 or 40 MOA.
Standard M98 after market triggers fits.
And in it's original configuration, it comes with a chassis system with a intergal mag well, the size makes it difficult to fit it to most stocks though.
But if you want a DBM unit for it, the CDI version can be made to fit.
Combine that with a Bix'n Andy M98 two stage trigger, a quality stock (McM comes to my mind), and a good barrel and you have the ultimate Mauser.
The price might become hard to swallow though.
The second best choice would be the current Double square Bridge Mauser design from Mauser, Prechtl or Ragnar Hansen.
These are extremely expensive though and Sandwarriors reference for 10 grand is about right.