Setup

This is just my experience with handling all of these models and such. I made a second copy of GTA:V and am specifically only modifying that one. I handle my testing through CodeWalker and by copying the model files, collisions, etc. over to alt:V.

For everyone else it can be a totally different experience but I'd just recommend a second copy of GTA:V so you don't screw up your working copy.

OpenIV

Setup OpenIV so that it uses your second copy of GTA:V.

This will prevent corruption of your game files and allow you to mod your game in tandem with CodeWalker and get your models to load in CodeWalker.

Get the download from links section.

CodeWalker

Setup CodeWalker so that it uses your second copy of GTA:V.

You can find pathing under options to select the correct version of GTA:V that you wish to use.

Get the download from links section.

Loading Models in Code Walker

You need to have a very specific DLC setup. Below is a link to an .rpf file that will have the setup that you need to achieve models loading in CodeWalker. Also don't forget to tick enable mods and enable DLC as well as select your DLC from the drop down menu.

File Tree

Here's a file tree that shows all the files necessary for making an interior. This can be seen inside of OpenIV.

└ mods/update/x64/dlcpacks                 
    └ dlc.rpf                                   
        ├   content.xml                               
        ├   setup2.xml                                
        └   object.rpf                                
            ├   MODELS / COLLISION FILES GO IN THIS RPF
            ├   your_model.ydr                            
            ├   your_model_collision.ybn                  
            ├   your_ytyp.ytyp                            
            ├   your_mlo.ymap                             
            └ \ _manifest.ymf

Here's a screenshot in OpenIV to help out.

Here's an .rpf file to help you figure it out:

https://drive.google.com/open?id=1TDdpJ0ciTAF2_-DKNewQc-9xBEDIboRX

Once you have all the above setup. You need to load your dlc.

Adds the dlclist.xml file to your mods folder via search menu.

Path is: /update/x64/update.rpf/common/data

Append your dlc name to the .xml file under mods to get it to load.

Example

If you need examples of content.xml and setup2.xml here's some gists.

  <Item>dlcpacks:/stuyk/</Item>
  <Item>dlcpacks:/paletobar/</Item>

<?xml version="1.0" encoding="UTF-8"?>
<CDataFileMgr__ContentsOfDataFileXml>
    <disabledFiles />
    <includedXmlFiles />
    <includedDataFiles />
    <dataFiles>
        <Item>
            <filename>dlc_stuyk:/objects.rpf</filename>
            <fileType>RPF_FILE</fileType>
            <overlay value="false" />
            <disabled value="true" />
            <persistent value="true" />
        </Item>
        <Item>
            <filename>dlc_stuyk:/paletobar_ytyp.ityp</filename>
            <fileType>DLC_ITYP_REQUEST</fileType>
            <overlay value="false" />
            <disabled value="true" />
            <persistent value="true" />
            <contents>CONTENTS_PROPS</contents>
        </Item>
    </dataFiles>
    <contentChangeSets>
        <Item>
            <changeSetName>STUYK_AUTOGEN</changeSetName>
            <mapChangeSetData />
            <filesToInvalidate />
            <filesToDisable />
            <filesToEnable>
                <Item>dlc_dnp:/objects.rpf</Item>
                <Item>dlc_dnp:/paletobar_ytyp.ityp</Item>
            </filesToEnable>
            <txdToLoad />
            <txdToUnload />
            <residentResources />
            <unregisterResources />
            <requiresLoadingScreen value="false" />
        </Item>
    </contentChangeSets>
    <patchFiles />
</CDataFileMgr__ContentsOfDataFileXml>