Relax buddy, its a bunch of guys chewing the fat over a rifle and getting excited.WOW! So much misunderstanding here.
What some oaf does in Pakistan is not a safe model of doable in the US.
A 30-06 chamber is flat out too long for 8x57. Just look at the dimensions folks.
To "rebore and rechamber" from 30-06 to 8x57 will require setting the barrel back and rethreading it. Then the oprod requires shortening because the gas cylinder is moved towards the receiver by doing the barrel setback. It's been done, it isn't worth the sweat or $.
Just rebarrel to 8x57, the barrels are available as noted by the OP.
Port pressure is a bunch of hoopla. HA HA HA. We won't being going to someone for our ammo. LOL.
Maybe if your not busy and know so much about it, you can install a Lothar Walther barrel for him and not charge him for the work.