Can I install an SSD in the late 2015 27" iMac?

I have a dead 2011 iMac (see my other posts) and I looking into replacement possibilities. I really want a new Retina 5K iMac, and whatever I get I plan to get as close to top of the line as I can. That being said, I want to upgrade the RAM and storage drive. I'm planning to buy the 27" iMac with the upgraded 4.0GHz GPU with 8GB RAM, the 2TB Fusion drive, and upgrading the graphics to the M295X video card. I'm not paying Apple $600 for 32GB RAM when I can get it from Crucial for $140.

My main question is, I want a 1TB SSD, but no way am I paying Apple $700 when I can buy the Samsung Evo 850 1TB SSD for $300. So if I buy it with the 2TB Fusion drive can't I just swap out the fusion drive and put in the SSD? As long as I install the OWC thermal in-line sensor for fan control I feel like I should be ok. To be clear I want to install it in the SATA port not the in the PCIe slot. I would just leave the 128GB SSD in the PCIe slot.

The reason I ask is that I can find no guide specific to the late 2015 iMac 27" A1419 EMC 2834. The guides I have found only show the late 2014 or early 2015 models.

- iFixit only goes to early 2015

- OWC doesn't list internal drives as an option to upgrade

I assume that late 2015 is the same as all the rest, it's just that the guides haven't been updates with the newest models.

Thanks for any help.