You could always make custom engines, fueltanks, etc. by yourself. Also, custom engines and performance parts mostly just need some code, it's easy actually. --- Post updated --- (unless you wanna be unique and realistic)
My current default vehicle is a rusty old 4x4 D-series. D-series 4x4, Locking hubs and diffs, H/L gearbox, complete with light bar and snorkel.