This page gives some details on how to modify the heatsinks for Compaq Proliant DL380 G1 servers for use in the AP550 workstation. It's a more economical option than buying from people who assume that limited supply automatically means prices must be sky high.
These mods are sufficient for fitment to the first cpu.
Side view after the above mods. This side view also shows the bottom row of fins removed, this is only required for fitment to the second CPU in order to clear the capacitors next to the slot.
Front view of a heatsink fully modded for the second CPU, with the bottom row of fins removed, and a notch cut out for one particular capacitor.
Detail of the notch mentioned in the caption above.
The manufacturer originally used some kind of adhesive on the CPU die. Cohesion is poor, so the heatsink is easy to remove. However, adhesion is very good, so it's very difficult to remove from the heatsink and CPU die, no solvent I have access to was at all effective, the only way to remove it was with a sharp knive and a very steady hand. It's possible to do without scratching the die, but with great care.
Additionally, although the heatsinks have cross cut fins which aids cooling area, they are a lot shorter than the AP550 parts (the DL380 is a rackmount server, after all). It's well worth making a baffle to ensure that the chassis fan draws air over the heatsinks, something simple made from cardboard is sufficient, and makes a lot of difference to the operating temperatures.
