Whatever you do, add ducting. The street material won't hold up at track type temperatures. In my experience with trying it, the binder seems to give up the ghost and the friction material crumbles. I went through a set of pads in 20 minutes when I tried regular street pads in the rear brakes of my Z.
When I tried regular organic pads they just turned into a paste that covered my rotors (and drums in the back I'd assume)
Metallic pads & shoes & DOT4 fluid let me stay out as long as I cared to for track days...but that was on a car that was less than 2500lb with me in it, and on a small track with only two points where you needed to do significant braking.
Can not help on getting pads but Use it as a no brake session. You may actually find you turn faster lap times. I had the exact same experience with my FC RX7 years back and by the end of the weekend on stock pads I was running faster lap times then I had been with "good" pads. It requires a change in driving style and the end result was I drastically reduced my brake pad usage and ware and tear on the car from that day forward due to me learning a new style of driving.
In October I did a 2 day HPDE event with my box stock 2011 Honda Fit (it's a long story - track car laid up). The OE pads were over 80% and I figured with a brake flush and low power I figured I'd be fine. About 5 laps into the first session - nearly no brakes from pad fade. I drove the rest of the weekend as Keith suggested - like I was driving a 1950's drum braked car. By noon Sunday, the pads were completely gone. I swapped in some parts store ceramic pads, which were cracked and badly pitted by later the same afternoon.
Bottom line - do whatever you can to get some performance pads in that thing.
Well, thanks for all the tips and suggestions guys - much appreciated! After calling around to pretty much all of the local parts stores I was finally able to figure out a passable solution for the day. PepBoys was able to get me a set of Akebono Ultra-Premium Ceramics, and I'm hoping that along with the OE pads, we can get this to work. Good news is it looks like we'll get heavy rain in the morning, temps in the low 50's/high 40's, this isn't a super-fast track (Talladega Grand Prix), and I'll be on Ultra-performance street tires, not slicks. So, all those items combined, I'm hopeful this will work out ok. 
Thanks again.
How did it go?
FYI In a pinch, I once used NAPA semi-metallic pads and they didn't make the entire day. Roasted them right off with 2 more sessions to go. I hope you had better luck than I did! This was on my 3,600 lbs (ish) Mazdaspeed6.
Curious how the Akebono ceramics worked, I did an HPDE with them on my E36 328i with street tires, the pads had serious fade issues and were cooked by the end of the weekend. They're a fine street pad but didn't hold up under moderate HPDE use.
Curious how it worked out here too, the Akebonos are great street pads but I have my doubts about track use.
Well... I'd love to give you guys a good report on this, but it will have to wait until next time. We found some seized suspension bolts (the eccentrics) and couldn't get the alignment anywhere near acceptable after lowering the car. We also found one damaged control arm bolt that had been replaced by the PO with one that was too small. We had to swap the rear subframe to fix everything and didn't get it finished in time. 
We'll probably arrange another day in the next couple weeks and I'll give an update after that.
Thanks again for all the tips though - much appreciated.
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