So I purchased my first Titan X SC because it was the only one in stock at the time. Now, two weeks later, I decided to purchase another one, but they only had the non-SC. I still need to call so I can verify my payment method, so I may cancel the order and get the SC when it comes in stock. However, if I decide to keep it, will I have any issues running the SC and a non SC in SLI?

Thanks.

I thought this didn't always work. Specifically, the gtx 970' I read a SSC won't sli with a FTW+. Or a FTW with a Asus Strix. Or did that change?

There should be no problems running these 2 cards together in Sli (they are based on the same reference design PCB).
 
The SC card will simply under-clock itself (this happens automatically, so you don't have to do anything)
and run at the same speed as the non SC model.
 
There is also a very good chance you can overclock the non SC card to match the SC model if you don't like it holding back the speed of the SC card.

MrImSoGood

SuperConker
The SC card will simply under-clock itself (this happens automatically, so you don't have to do anything)
and run at the same speed as the non SC model.

No it won't. Nvidia cards have stopped doing that for years. Clock speeds will run independent of each other

Not according to this post.