Powerstop was directional and I think mine are just like yours, I'll look today when I get off. According to Powerstop the holes allow the gases to escape and the grooves "cut" the pad a little so you always get fresh pad material. I will say they do help alot, at least in my case they did.

 

Also good job on that frame! I still have to do the front of my frame after I fix the time holes in the horns on the front.

 

You're right about all that, doubt it makes much difference, just want the gas/heat/dust to head out to the atmosphere and away from my hub bearings if possible.The grooves are directional and go right to the edge of the rotor, some smart engineer had a plan. I put oversized rear wheel cylinders on, which helped a bit, won't do too much more than that. Drive a lot of bad winter roads, I'll let the discs handle the bulk of the braking, help them out best I can.

 

Something else I've always wanted. Had these old 70's tow hooks for years. The mount is patterned after the Gen II Off Road hooks, 3/16 plate/angle. I added some angle welded to the frame cross bar to bolt them through. Since welded a tab to the top of the angle for a third bolt to pass through.