How to get 60 FPS at 4k with a GTX 1070 on just cause 3?

Solution
I can't recommend 4K for this game.

Performance-> https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1070/17.html

1) MONITOR-> choose 2560x1440

2) HDTV-> setup for 1080p

4K simply doesn't make sense. On an HDTV you need to choose either 1080p or 4K resolution, but at 4K the game settings have to be dropped to the point it looks worse (in fact, if not sitting closer than 1.5X the HDTV diagonal you probably can't benefit from 4K resolution anyway).

And on monitor the difference in visual quality is very small so 2560x1440 makes the most sense in terms of FPS and settings. Depending on how often the FPS drops 1920x1080 may even make sense for a smoother experience because as stutter is more important than slightly sharper image...
I can't recommend 4K for this game.

Performance-> https://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_1070/17.html

1) MONITOR-> choose 2560x1440

2) HDTV-> setup for 1080p

4K simply doesn't make sense. On an HDTV you need to choose either 1080p or 4K resolution, but at 4K the game settings have to be dropped to the point it looks worse (in fact, if not sitting closer than 1.5X the HDTV diagonal you probably can't benefit from 4K resolution anyway).

And on monitor the difference in visual quality is very small so 2560x1440 makes the most sense in terms of FPS and settings. Depending on how often the FPS drops 1920x1080 may even make sense for a smoother experience because as stutter is more important than slightly sharper image.

You'd have to experiment though. Maybe use Adaptive VSYNC, then tweak 2560x1440 until you rarely drop below 60FPS (on 60Hz monitor).
 
Solution