Every processor I could find that someone has slapped into a Mac Pro is listed in the Mac Pro CPU Compatibility Guide in my signature. I did not find anyone who had tried the two processors you mentioned.
So unless someone answers you definitively, you'd be the first that I know of to attempt to try these out. Therefore, if you do try them, I'd buy from a vendor with a good return policy in case your MP doesn't boot.
The E5-2670 v2 may be a contender. Based on this old blog post from OWC I suspect that they were going to try it out, but unfortunately as far as I know they never provided an update.