Early Intel CPUs, ("Prescott P-4" and "Pentium D" especially), drew more power, and hence made more heat than the later 65 watt "Core 2 Duo" offerings, which are all 65 watt TDP.
Accordingly, the early heatsinks had a lot more cooling area, (read "a lot more metal"), in them.
So, an early heatsink on your C2D, would cool better than its own supplied HSF.
I say this from personal experience, since I have a HSF from a "Celeron D", (86 watt) on my "Pentium Dual Core E2200", (65 watt TDP), and it improved the cooling from the E2200 stock unit.
With all that said, the earlier HSFs still have the annoying 80 mm fans, which have an annoying sound.
Please note that when I say, "cools better", that I don't mean, "cools great".
Also, this is a hardware question, and consequently might have been better placed in one of the hardware forums such as, "General Hardware" or "Processors, Chipsets, and Motherboards", or even "Overclocking, Cooling, and Modding".