I have a T3500 completely stock other than a 750w corsair PSU.
The CPU is reaching around 90 Celsius routinely and this is an issue.
Can I get any aftermarket Passive CPU heat sink that will do a better job.
I'm not aware of any aftermarket heatsink that can be mounted due to the special heatsink mounting bracket that Dell uses on the Dell T3500/T5500/T7500 series. You can buy a special heatsink on ebay that is a Dell original heatsink with a special fan mounted on it. You might be able to mod your own heatsink. Go to ebay and do a search for: T3500 Super Heatsink