I ran a Blizzard 060/PPC with BVision in my A1200's case by peppering the trapdoor with holes for ventilation and adding a small fan underneath the upper back vents. I didn't seem to have any overheating problems, but I may have been lucky in this. I also very carefully soldered some wires to the power socket input pins to connect to the pins on the Blizzard, although if anyone was going down that route I'd very strongly advise to check and double check the voltages before plugging it in...
Cheers,
Nigel.