OP, about 35 years ago, it was not that uncommon to see those lovely Brazilian 1908 and 1935 Mausers stripped to their receivers and made up into fine hunting rifles.
They were never cheap but the actions were tight, extremely well made and square to center.
They were a gunsmith's dream. I remember a fellow in Kelowna, that brought in a crate of them to convert into several different calibers. I was lucky enough to get all of the stock/metal bits from him before he tossed out the bands and cut up the stocks for firewood.
I still have a barrel left from him as well but I had to pay him $10 each for them at the time.
Up until a few years ago, there was a fellow from Kamloops that would come to the show with a half dozen of these actions, new bolt handle, rear bridge machined flat, the ring and bridge d&ted and the blue matched up perfectly.
He wanted $275 each for them. At the time, I didn't have my own tools and bought one to build up. I couldn't get the work done and pick up an action that cheaply.
That rifle will make a fine sporter. If the barrel is in excellent condition, like so many of those rifles were, it will be very accurate as well.
There is no cheap or feasible way to put that old girl back into full military configuration.
Get a decent stock for it, wood or plastic, your choice.
Finish the job. Do it right though and make nice. You may want to cut back the barrel to a more manageable length as well.
Now, if the stock and bands are all still intact, put them up for sale on the EE. They won't last long. If it's in good shape, you should be able to get enough out of it to pick up a 95% finished and fully inletted walnut or even a laminated stock from Boyd's in the US.
Right now, the rifle is a beater. A virtual ugly duckling, ready to become a swan.
The mods to that rifle were probably done 35 - 40 years ago.
The Brazilians were considered to be the cream of the milsurps for the basis of a fine custom sporter.
They were arguably some of the best and most well finished rifles every produced by Mauser for any military.
Do that old girl a favor, and dress her up.