I just upgraded the CPU in a Dimension 8300 to a Pentium 3.0HT, and
swiped the heat sink from a Dimension XPS Gen 2 system. It is the same
heat sink with copper heat pipes used in the faster 3+GHz Dimension
8300s. It is also the same as used in the Precision 360, Optiplex GX270
(tower model), and newer Dimension XPS systems in the monster blue or
black case. No surprise, as the motherboards all use the 875 chipset
and they look more or less the same, and use identical mounting plates.
The only difference is that some boards have integrated ADI sound and
some do not.

The CPU I took out was rated 2.6HT, and it had an all-aluminum heat sink.

The fan-and-green-cowl for both types of heat sink is the same... Ben Myers