I just modded a Thermaltake Volcano 6Cu heatsink. I removed the very noisy 60 mm Thermaltake / Everflow fan and the fan mounting plate.
I then found four small right-angle brackets and drilled the aluminum heatshink and used pop rivets to attach the brackets to the heatshink. I then attached an 80 mm Panaflow # FBA08A12L with four screws & nuts.
The mod took around 1/2 hour start to finish. I am planning on using it with my Athlon 1800+ and see how much quieter it will be. I would like to get a hold of an 80 mm fan with the 3-pin for the MoBo RPM monitoring (MikeC has some for sale, but I need to get to his house).
I'll keep you informed.