Josh, I gotta agree with Hogghead on going with a short action as the best way to start your 260 Rem build. With the LA You will just have more weight added to your project with no benefits that I can see for the bullets you plan on using.
As a side note, A Kimber 84 Montana might fit your needs without going the semi-custom route and last I looked it came in .260 Rem, 22" SS barrel, syn stock, all at just over 5 lbs unscoped.
