My plan for locating a tank or two in the stock location died the moment the stock fuel tank hit the floor. The service manual doesn't really do a good job of representing scale to the reader, and I got tripped up by that; the stock tank is incredibly shallow (but wide), and doesn't get much deeper at the saddlebags. They've relied on the oddball shape of the tank for the volume of fuel that fits in there. So, out with plan A, and on with plan B: we're carving the rear spare tire well out of the car, and I'll be putting an ATL 15-gallon aluminum fuel cell back there that I ordered from OG Racing, along with a nifty battery kill switch with a detatchable handle. I have all the fittings needed to mock up the pumps now, so once the cell is here, I can start mounting everything to determine line routing.
If anyone's curious, I've thrown a gallery together with pictures of the build-up progress so far, the parts I'm using, and the parts I bought with the best intentions of using but ended up selling or otherwise finding a new home for.