oddly enough, I just done this last night.
THE CONSOLE/JUMPSEAT should be installed first with the back of the seat up so it will have adequate travel room when needed.
1. Take an air hammer and push the gas tank humps in the floor pan toward the back of the cab as far as you can get it (about 3-4").
2. All the pushing of the metal will usually create an "upward" hump in the metal, if it' not a big deal to you just leave it alone. If it bothers you, you can push it back down with the air hammer. (its under the carpet and behind the seat of a reg cab, no one will see it.
3. Slide the inner seat rail (the TOP one closest to the console) all the way back and take a grinder or Sawzall and cut it at a 45 degree angle from the end top to bottom. (DO THIS ON BOTH SEATS)
4. Place the bolt of your choice in the inner seat tracks and put a couple of tack welds around them to hold them in place, because once they are positioned in a regular cab there isn't enough seat travel to expose the bolt holes for installation.
5. after all the holes are drilled and all that is left is to bolt them in and enjoy.... take the time to pull the carpet up and spray some spray paint (or something) around the your holes, so they don't rust......and remember all that REQUIRED pounding you did your floor pan to make room???? It chipped a ton of paint off (usually to bare metal) so spray it too.
NOTE!!! These seats weren't designed for this truck.... having said that... a little known secret about the OBS trucks is that the trans tunnel isn't center in the cab as it appears to be..... the factory seat brackets for OBS trucks do a great job of hiding this, but unless you plan to build all new brackets for all three pieces (which would be a nightmare) you will have seats that sit closer to the passenger side of the truck. When you finish this project with the NBS seat brackets you will have 2-3" of clearance between the driver seat and door, but the passenger side will be touching slightly.
All in all, the off-centered seats do bug me to an extent, but not enough to build custom brackets for all of it to be perfect. The seats are amazing upgrade though, especially in a 5-spd truck that came with a bench seat. I love them.