I have run mine with flux core.
I would use the flux core, and preheat as described by yomax4.
I have welded metal that thick in the past, without any problem.
Keep in mind you will at some point run up against the duty cycle, and the welder will shut down while it cools.
You can't weld with this machine set at the higher limits for hours on end. But, you can do this kind of job with it.