I had an "itch that I couldn't scratch" to build a custom .308 Mauser out of a Mod.48 Mauser (Yugo). Started with a really cherry barrelled action and though I would get out "reasonably" cheap, since my gunsmith who built the rifle is a good friend. I had to argue with him to take more money for his labor, since he worked for almost nothing. The rifle turned out GREAT, but cost a WHOLE LOT. Just parts like a Timminy trigger, safety shroud, new barrel, stock, scope mounts, scope, etc., etc. just ATE UP MONEY. Labor would/should have been through the roof!!!!!!! If you have to pay to have the bolt handle moved or reshaped, the bolt lapped, the rifle readied for good scope mounts, inletting and bedding the stock, installing shroud, fitting the barrel, and tuning new trigger, you are in for a WHOLE LOT OF EXPENSE. If your heart is set on a custom Mauser, scout the shows for one that is close to what you want and start there. They ARE out there for a lot less than you can have the work done for. Take it from one who wouldn't listen when the same advice was given to him!!!!! I am not proud of my mistakes, but hopefully someone can learn from them.
While I do love the resulting rifle, if I had it to do over again, I would just go out and buy a Remington 700 or something similar. It would be MUCH CHEAPER, and still shoot better than I do.
Think it over carefully before you begin. Didn't mean to lecture, but hate for someone to get into it without their eyes being WIDE open. Best of luck to you and Happy Trails.......