If you've ordered the HMMWV from Rico Reyes in Cali Cantinos, prepare for a long wait. It's never gonna get there and you've lost the money you've put down. In vanilla you can only have 4 types of cars, the GAZ69, the Willies Jeep, the URAL and the APC. There are 2 other cars in the code, (Hummer and FMV A1) but they are not available anywhere(unless you play with the BFX mod, if I may be bold and mention my own work
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The unofficial patch actually fixes a lot of those translation errors, along with the M4 butt bug, the other things you mentioned and various other issues. The naming thing is my mistake, mebbe I should've named it something above 1.11. I think it's up to 0.98 and I still contantly find things to fix. When I'm finished with it I'm sure it'll be up to 1.12 or something.
The uniforms can be used to gain access to towns that are hostile to you. If you play for the Rebels and are at war with the government, put one one and you can enter those government controled towns without triggering combat. But if you get too close to the police or soldiers, they will turn hostile.