Doesn't anyone ever use Google?

I typed in this:

heatsink spacing 1156 mm

and the first thing that popped up was this article at TechPowerUp

http://www.techpowerup.com/tags.php?tag=XIGMATEK

"With a hole spacing of 75 mm, LGA-1156 is somewhere along the way between LGA-775 with a spacing of 72 mm, and LGA-1366 with that of 80 mm."

That's why new brackets are needed and why you can't swap coolers without new mounting hardware. The holes in the motherboard are unique for socket 1156.