Hello all-I've just removed countless 1x12x12 pine boards from the attic of our house. Instead of letting it go to waste, I've decided to rip all the boards down to 3" wide planks, cut out all the waste, and lay them in a rustic garage setting that I'm building out. There's a new raised subfloor in the garage that I've insulated with vapor barriered insulation, and now I'm close to getting ready to install. My thinking was to use my finish nailer to attach all the boards to the floor. It's not going to be critical that these are pristine. In fact, with all of the old nails I've pulled from the old boards, it should look pretty beat up and "barny" if you will. My questions are these:

1. Is there a better way to attach to the floor that a slightly set finish nail on the face of the boards? Do they have small pneumatic flooring nails that are ribbed for extra grip? I am planning on doing some sanding to create a slightly uneven look to the boards and would need a little wood to sand without too many nail heads to worry about.

2. Since this wood is older than dirt, I'm assuming it's pretty well seasoned and I will allow it to acclimate in the garage before I put it down, but should I try to space the boards with a 1/16" shim to allow for expansion or will the 1/2" at the outlying edges be enough to absorb expansion?

3. Do I need to put down tar paper over the subfloor even though the insulation batts have a vapor barrier on the already?

Thanks, brian