-I have a 308 action and an extra magnum bolt face bolt any issues with using this for a 350 rem build? I assume there is no difference in the action itself

I ended up in the same situation as you about 15 years ago. First tried finding a non-magnum bolt but the search was fruitless. Ended up having my gunsmith re-chamber to .30x.350 Rem Mag (cheaper than a new barrel). Since my little thumper has a hair more case capacity than a .30-06, that is what I use for load data. That little sucker roars like a lion, breaths like a dragon, and sure is a lot of fun to shoot. I have 4 M600s, a 6.5 mag, a .308, a .30x.350 Rem mag and a .350 Rem mag. If you have not shot a M600 in .350 mag with 250 gr bullets before, be prepared see God. I ended up installing a receiver sight on my .350 because of scope cuts. Think twice before going all the way to .350 Rem Mag.

Good luck and please let me know what you end up with.

George

I have a 350 Mag with a Kevlar stock (as if it wasn't light enough as it was)

I now have a 1x4 Weaver scope on it. It has plenty of eye relief. I only shoot 250 grain bullets in mine anymore (I tried a few lighter bullets but could not see a reason to shoot them.) Hornady Interlock are my favorite. But Speer 250's shoot just as well.

I believe tat you could re-barrel it and it would work ok. I'm thinking the feeding is controlled by the magazine lips.

Get a Magnum follower from Numrich and should be all you need. Mine feeds perfectly without lip alteration.
George