Glass and pillars would not hurt . I have had numerous 600s of various calibers. Never seen one which had a action to stock fit that instilled any kind of confidence in the gun.
As for tightening I like to start the screws then tighten the front down good and tight 40 to 50 in pounds if you got the wrench. If not about as tight as you can get them usually is 40 ish on the slotted screws. The rear action screw is rather small and not doing much for seating the action which is why I snug the front down first. The rear screw just til it is tight all it really does is hold the trigger guard in place.
I have a 243 600 which I restocked in a brown precision stock. Bedded it tight with a front pillar free floated the barrel. I run the front screw at 50 in pounds rear just tight. Gun shoots from real good to holy chit good.
Finally got it done:
1. The screws were not even snug!
2. Bought a FAT wrench so I could accurately torque.
3. Tightened the front to 40 in-lb.
4. Tightened the rear action screw to 30.
At 50 yards: 1", 3-shot groups for 3 groups. Problem solved!
However, now I have another problem. New problem, new post over in the reloading forum.