Woohoo, post bump
Seriously though, I have to post this message as yours is misleading.
You can have ALL cars in one resource, and there are two main ways to do so. Let me elaborate:
First One
This one is an “easier” one, and it’s explained in detail in this post
Second One
The second one is somewhat similar, but the actual process is different and that’s how I personally prefer merging vehicle files together.
As always, don’t forget to merge all stream folders first lol
Next, open each .meta file individually and copy the “contents” to a single file. The exact method varies per file, but it’s normally the <Item>*</Item> part after the CArchetype definitions and whatnot. I cant really explain this, but it’s sorta self-explanatory once you try.
It’s also a good idea to run the new .meta files through an XML Validator as it’ll pick up any syntax errors you made.
As such, there is no need to have multiple resources for each vehicle individually. You can, if you wanted to, merge literally every single vehicle into one resource and it WILL work as long as it’s done properly. Not only does the overall resource count go down that way (having too many leads to some weird issues), it also makes client loading time arguably faster, having to index fewer (but larger) files and only mount data from 4-5 files at startup instead of 40-50.
P.S. You do need to be careful with SirenIDs and other IDs specifically, though - make sure none are duplicated. Easiest way to search for them is using VSCode to look inside *.meta files for a specific number.