Some options for your build
First thing-don't buy a pristine military Mauser in full trim and cut it up-they are getting rarer, expensive and these days it just doesn't make sense to destroy the remaining history out there. Buy a beater rifle with a shot out barrel or one some other guy bought and cut up. Every one I have bought to sporterize I got on Sarco or Century junk rifles without matching numbers or any other worthwhile, collectible value. I believe both of these companies still have some rifles in this category. If you are just looking to get some experience a used savage is a good choice and will usually outshoot most military surplus rifles.
I have built several Mauser sporters on Yugo actions and one small ring Turk. For ease of conversion and cost reasons you might want to look into a 6.5-06 Ackley improved or one of the other similar rounds without a belt.
For the 6.5-06 you are only giving up about 150 fps for a 140 gr bullet and less for a lighter bullet. You use much less powder per shot and brass is much easier to find. You can use military 30-06 brass and run it through the resizing die (i do it with 308 to 260 without any problems). You do have to trim a far amount of length off. The bolt face and extractor doesn't have to be re-sized and the ackley improved cases actually have a lot less bolt thrust than the conventional rounds.
Mauser were made by everybody (i have read over 100 million were produced). I would recommend just about any of the full length large ring 98 actions-German, Check, Argentine, just about any of them. The yugo 48 actions are intermediate length and too short to feed long bullets in a 06 case, the Spanish might be too soft, most of the Turks are small ring (and some other latin/south American mausers also).
First-buy a book or two on how to do it-Kuhnhausen's book is good but really technical-wal mart sells a book called gunsmithing made easy that has a very good section on doing what you are talking about.
You will have to order a custom barrel from shaw or douglas. If you are going to do more than one gun buy your own barrel vise, action wrench, scope mounting jig. Don't buy a finish reamer, rent one from any of several different companies. If you are just wanting this one rifle pay a professional, it will be much cheaper (it really takes at least 3 rifles to pay for the tools-but buying tools is fun). Unless you are an accomplished welder get the bolt handle turned down by a professional. Buy a stock from boyds or richards microfit. Have a lot of fun.
The easiest route might be to buy a 'bubbaed' rifle with the original military or cheap barrel installed but most of the hard work done like the bolt handle. This are almst always cheap and readily available at most gun shows. There are almost always actions for sale on gunbroker also. But you need to know what you are buying to go this route-so buy the books first and then figure out what you doing. Kuhnhausen has a complete list of good actions.
