What you have is a Brazilian made Model 1908 rifle version.
Most of the 1908's were made in Germany by DWM and they're famous for their quality.
Later on, Brazil started making the rifles in Itajuba, and the quality wasn't as good.
By quality I mean the fit and finish, not the strength.
Originally, the Brazilian 1908 was chambered in the 7mm Mauser.
Later, rifles were reworked to 30-06 rifles because we gave them large quantities of surplus ammo.
Yours is one of the re-works.
In order to convert to 8mm Mauser you'd need a new 8mm barrel correctly fitted and head spaced, not a new bolt.
If you have a 30-06 rifle that needs a new bolt for some reason, you'd have to have the rifles head space checked and possibly the barrel re-set to correct it.
You SHOULD NOT just buy a bolt and put it in. The head space can be off enough that you could have an exploding rifle near your face.
The only way to know is to have a gunsmith check it with a head space gauge.
The later Itajuba rifles were more or less interchangeable with parts from the earlier DWM made rifles. Note that as always with old guns parts may need adjusting to fit and function correctly, and some parts may not work in some rifles due to wear of the rifle and the replacement parts.
For parts for your rifle, you can buy DWM Model 1908 or Itajuba 1908 parts, or in many cases, almost any large ring Model 1898 Mauser rifle variant parts can be used.
Here's sources for parts: