Let me look into modding communities. For GTA V, modders often replace vehicle models using mod tools. Sometimes they use .rpf files to hold their changes. However, the name X64a.rpf seems generic. Maybe it's part of a specific car mod. I should check if there's an official source for this file. Also, looking into user reports on forums, like the GTA5-Mods website or Reddit, could help. Are there any complaints about this file?