Getting to 3.5Ghz *3.2 is more reasonable* would require a lucky chip if you're going to be doing air cooling. I'd go for an X48 based motherboard if you have plans for crossfire, otherwise a $120 P45 based board would be fine for single card solutions.
As for heatsink, the Core-Contact Freezer should be great for reaching high clocks. I like my Ultra 120 Rev. A with a Nexus Fan, but there are plenty of choices. HDT-1283, is another good one.