OK, I managed to find some time to replace the guts of the server with my old hardware and install the new 92mm rear fans. Here's a few photos of what transpired.
Here are the two 92mm fans installed directly on the backplate. As you can see, they aren't exactly straight. I thought I was using some sharp drill bits but it turns out they weren't quite as sharp as I thought. The result was that the drill bit wandered slightly when I was drilling the 2nd hole, causing the first fan to line up slightly crooked when I installed the fan screws. Fortunately there was enough space for both fans even with them being askew and they were still fairly well centered over the fan grate on the back. The rear fan brackets are each held in place with a single screw so they were simple to remove. I lined up both fans and then used one of the fans as my drill guide using a drill bit the same size as the screw holes. I then enlarged the hole with a slightly larger bit so the screw could pass through freely.
Here's a shot of the 120mm fans mounted on the Norco fan wall with the fan grates installed. They were only $4.99 for a set of three from Newegg with free shipping. They did not come with fan screws, but I had enough on hand that it wasn't a problem.
Here's the finished installation. I'm using an Asus F1A55-M LX micro-ATX motherboard with an AMD A4-3400 CPU and 8GB of GSkill RAM. The motherboard only has six SATA ports, all of which are being used. The nice thing about using controllers such as these is that the breakout cables required make cable management a breeze. I used 0.5m cables on the side nearest the controllers and 1.0m cables on the farther side. The long cables have a protective sleeve which is a plus because the fan wall openings on that side have sharp edges. The openings on the other side have a rounded edge so they won't damage the cables. I thought it strange that they did that on one set of openings but not the other. In addition, I have two Supermicro AOC-SASLP-MV8 8-port SATA controllers and a Promise SATA300 TX-4 PCI 4-port controller, of which I'm only using two of the available ports. I'm also using an Intel EXPI3901CT NIC instead of the onboard Realtek NIC. I like this motherboard better because the CPU cooling fan is now aligned directly with the case fans whereas it was aimed side to side instead of front to back on the Supermicro board.
Here's another shot of the finished project. You can't see it but I'm using the breakout cable for the front panel instead of the original ribbon cable that connected to the Supermicro motherboard. There are quite a few connections that will go unused if you're using a non-server motherboard like I am. I couldn't use the power connection because it uses a wider connector and the pins are spaced further apart than the header pins. It's not really an issue because you know when this thing is running and a little LED isn't needed to tell you that it's got power.
The Asus motherboard only had a fan header for the CPU and one case fan. Fortunately, all of the fans came with 3-pin to 4-pin Molex adapters and the two Molex cables from the PSU each had an unused connector. I daisy-chained two of the 120mm fans and connected them to one of the free connectors and installed a splitter cable on the other cable connector. I connected the remaining 120mm fan to one of the splitter connectors and one of the rear 92mm fans to the other connector. The 2nd 92mm rear fan was connected to the open case fan connector on the motherboard.Edited by captain_video - 4/22/13 at 4:11am