What you'd probably want to do then is:

1. One of you make the post, along with splitting it's rewards.
2. Whoever didn't post it, resteem it.

It'll be a single post, no duplicate content, and all of both of your followers will see it.

You could even get fancy and create a 3rd account and both use that to post, use it as a blog/pen name, and always specify a 50/50 rewards split between your two primary accounts :)