You can use the HDD, but the RAM is bespoke to the iMac range at the time- it is also has the shorter laptop dimensions. The Processor i5-4670 could be used - although getting a compatible motherboard may be tricky.
I would remove the WIFI and bluetooth module as these can possibly be used with an adaptor board and fitted to a PC motherboard.
Your iMac has a graphics card that is built onto the motherboard and this can not be used. The monitor cannot be used - although some folk with skills have got iMac monitors running with some technical hacking work and soldering.
https://everymac.com/systems/apple/imac/specs/imac-core-i5-3.4-27-inch-aluminum-late-2013-specs.html
For compatible pc hardware that would work with your iMacs i5 processor, see the following two links for motherboard hardware (note that most of this is now obsolete and may be difficult to find)
https://www.tonymacx86.com/threads/building-a-customac-buyers-guide-september-2014.151979/
https://www.tonymacx86.com/buyersguide/march/2016/
You can also try a search on ebay or Amazon for H81 motherboard and B85 motherboard. Most will work, but a few may have issues - ask for further advice if required.
For WIFI and Bluetooth use the following forum:
https://www.tonymacx86.com/forums/network.15/
For graphics support, you can run the Integrated HD4600 graphics on your iMac Processor, but for something more powerful, you will need to add a discrete card, models like nvidia GT640 were popular at the time but these are really difficult to find. nvidia GT750Ti are power efficient for more general use and can probably be found used for a reasonable price used (avoid ASUS Strix models with the VGA port - not macOS compatible!)
Other compatible cards are listed in the buyers guides. One thing to be clear about is that macOS GPU support is dependent on the version of macOS that you intend to run. You cannot use a new compatible card with an older version of macOS. There are additional nvidia drivers in the download section that cover all the models of cards listed in the buyers guide old and new. AMD has a dedicated section in the graphics section. AMD cards have traditionally worked well in OSX, but the last 5 years or so getting pc cards to work has been difficult. There are signs that this is about to positively change but the cards are hard to get at retail due to cryptocurrency miners.
https://www.tonymacx86.com/threads/radeon-compatibility-guide-ati-amd-graphics-cards.171291/
iMac case mods:
https://www.tonymacx86.com/forums/imac-mods.135/
If using a PC monitor then use a digital connection like DVI, HDMI or DisplayPort between computer and monitor. It is also worth having a USB keyboard and mouse for the installation process. Your existing bluetooth/Wifi hardware can probably be adapted to work, but it may or may not work in the pc motherboard UEFI/BIOS or until you get to the desktop - YMMV.
Hope that this offers you some good starter pointers and lets you consider or at least plan your way ahead to building a computer that runs macOS.