i'm using stock cooler with 333*10.5 = 3.5Ghz 1.35vcore
and using KVR too. don't worry i just like to keep poisoning people,
wanna bring back the OC scene just like during single core/ dual core/ X2 era 

yup with E7400 i can go up to 344*(cpu multi) 
err... which board do you referring to...

mine was ASUS P5 G41T-M LX
http://valid.canardpc.com/show_oc.php?id=2549200

that board was never designed for OC purpose bro...
if you want a good OC mobo (775 socket) try find used P45 chipset. example :
1. ASUS P5Q Deluxe(600 ++ fsb) LINK
or 2. ASUS Maximus LINK (easily reach 600 fsb)

stock cooler as i don't need 3rd party cooler for such voltage + such clock.
btw this OC on this cheap mobo is just for fun 

G41 was never designed for OC. 333fsb is consider very ok already for that mobo
btw you can try find max fsb for that mobo,
lower the ram divider and cpu multiplier, increase the htt.

333 is stock fsb for C2D E8...

you should try yourself bro.
as i suggested before, try find max HTT@FSB for that mobo.

since that mobo can run 333fsb, you can start from 334fsb onward
increase the HTT step by step.

let say 335-->340-->345-->..............400
i doubt that mobo can reach even 350fsb...