Taylor,
First if you are not going to pedal back up the hill one chainring will do fine. However if you just want to muscle back up then one will do fine as well. Race Face, shimaNO XTR, Tru- Vativ, AC, and Profile, all make good DH cranks. However if you want the most bombproof DH crank get the Profile. I also would not worry about weight on a DH rig after all you are going down the heavier the better. As far as body armor Dainese, Fox, and Answer makes good stuff. IMHO I would go with Fox after all the make motocross stuff I do not think they make crap when it comes to this stuff. Triple clamps are a good idea for pedals as you are not locked in if you have to bail at 50+ mph. Odysey makes a pedal called the triple trap old school BMX guys used them and so did I. They also make a pedal called the Black Widow that is superb but GOD have mercy on your shins if you slip the pedal. Also GT platforms are good alot of slalom guys use them cause you can replace the spikes and get bigger ones if you want them. As far as the best tracks well IMHO any track that is long and steep and offers a ski lift back up to the top is good. After going down for awhile the last thing you want to do is pedal back up especially if you have a DH specific rig, because they climb like s**t. There are of course other options on pedals and other DH stuff but those are a few I could just rattle off. Hope this helps.