From my experience with both a 27" barrel and a 30" barrel velocities weren't all that different. You'll see anywhere around 2950 - 3050 fps with a 140g bullet.
As for the action I'd recommend the Stiller Predator long action with standard mag box or a short action with a wyatts mag box cut out.
Price wise if you bought every part yourself and had the smith put everything together here's a ball park of what I would charge.
Thread, Chamber min. headspace, Fit, Crown, 320 grit finish, Engrave $200
Pillar Bed a fully inletted stock $175
if wanted $175 - $200
Odds and ends such as installing trigger, mag box, scope mounts ect. $50
Talk with who's going to be doing the build and tell them what you will be supplying yourself and what you'd like done. I normally give a very close estimate before starting any project, this way the customer isn't surprised at the end when he sees his invoice.