The 7mm STW is a great cartridge. For long range target and hunting, you might want to look into the heavy bullet options. They range from 175 grn to 195 grn projectiles. For some of these, you will need the 1:8" twist barrel.
As for the action, any of the Magnum actions will work. I like Winchester M70's, but a Rem M700, Weatherby, Savage, Howa, or Ruger will work. One of the draw backs will be the magazine length. Most are limited to just over 3.6". Some of the 7mm STW's have free bore. For my M70, i had a Wyatt's box installed, so now I can go over 3.8".
My question, is this Rem 700 Tapered a magnum action? If not, that is more work to open the bolt face, work on the feed rails, the magazine, and so on.
For me, if I was to do it today, I would go custom. Due to the heavy bullets available today. For the price of a Sendero, you can have a nice custom for a bit more. You supply the action, get it trued, trigger, barrel, stock, Wyatt's box, the whole nine yards, and you are good to go. It will be over the price of a Sendero, but it will be made the way you want it and do what you want.
For the Sendero, the barrel is either a 1:9" or a 1:9.25"/1:9.5" twist. This will limit you on the heavy bullets. It should be able to shoot the 168 grn bullets fine, and some of the 175 grns too. The question is, how many rounds down the pipe? How is the trigger, does it need other things?
Hope some of this helps.