It can support dual external 4K displays at 60hz. If the internal connectors are the same as the 4K model. The only reason I could see it not working is if Apple did some software tweak to prevent it.
Looking at the pictures I can find of the display panel connectors for a 1920x1080 iMac. They look physically different than the 4K. But these panels I found are listed for up to the 1920x1080 2015 model. The connectors are 30 pin in 1920x1080 and 60 pin in the 4K 2017.
You can always open it up and see if the connectors are the same. 4K 2017 pictured
For the 2015 1920x1080 connector see the attached Untitled-1.jpg
That can just mean the displays use different cables. What really matters is if the motherboard connector is the same. The second attachment is the best of the 4K 2017 iMac Motherboard connectors I found on iFixit. There others at other angles on their motherboard replacement guide.
You'd have to check if the 1920x1080 2017 are the same. Both 2015 models look like the motherboards may have the same connectors but the pictures are not detailed enough to be certain. I found none for the 2017 i5-7360u model.
While there is always the risk of damage. I think the biggest risk is having to eat shipping fees and possibly a restocking fee if it doesn't work. You'd need the panel and display ribbon. The panels look to go for around $200 to $250 on eBay, ribbon cables run $25. As far as I can tell the 2015 and 2017 4K iMac use the same panel based on connector appearance.
I suppose you could buy the ribbon cable first and see if it plugs into the motherboard.
All you can do is collect all the data you can then try at your own risk. If it works you'll get huzzahs and a deal on a 4K imac. If it fails you'll be out some money.
As an interesting note. The i5-7360u in the base iMac has a higher MSRP than than the i5-7400 $304 vs $182. So, Apple spent more money just to hobble the base iMac. They could have saved money with the Pentium G4560 for the same result.
