I have a vintage Remington model 30 express in 30-06 that I have just removed the scope mounts on, and the a##hole that mounted the scope (Many years ago) put 4 un-centered tapped holes in the front of the receiver. The Stith mounts require three, so I dont know what the other is for. Is it feasable to have the existing holes welded up so that I can properly mount a more modern scope?

Yes, they can be TIG'd up and then redrilled and tapped. The metal finish will have to be removed before welding. Just make sure the person who does it for you knows what they are doing.

It really irks me when your village "gunsmith" swiss cheeses a gun in an attempt to get one or two tapped holes done up. I've fixed some pretty buggered recievers, but I wish folks would just do it corectly yhe first time and not get in over their head. I usually see multiple hosed up holes, menaing they should have stopped when the first one started to go south. Oh well, enough ranting for now.

I did two Swiss cheese drill and taps at first.
Later I was drilling without a fixture, just in the mill, and I forgot to start a hole with a stout drill. That hole was slightly off. I modified the scope mount and glassed the mount to the receiver so it can't slide around.

I know where those two Swiss chese rifles are, with scope mounts covering my sins, and I am going to get them out and TIG weld up the holes, re drill and tap, and cover them back up with the scope mounts. It bothers me knowing they exist.

ALWAYS CENTERDRILL!