1: you're unlikely to be able to tell the difference in wire size with the seat-of-your-pants-dyno, but do avoid buying cheap wires. cheap wires increase the chances of arcing. If you really want a smile on your face, re-gear the axles. right now you have 3.55 gears. but it's complicated because you don't have an overdrive plus the dana 35 is not worth throwing your money at, so that needs a axle change too. it's a slipper slope.
2: that's literally the only rear window available new. they are... ok. if you intend on tinting it, be sure to do that while it's still out of the truck.
be sure to start yourself a build thread