modding gta sa is complicated, because, u can add a lot of vehicles if u play in sp, but if u play samp. U have to know wich cars are used in the samp, and put cars who doesnt affect to much the game inself, for example, dont change a clover for another, because, is a car u can modified a lot in the transfender.
for example : buffalo = shelby gt 500 Eleanor = transfender = dont crash. why, because u can only change the wheels. low rider, color and nitro. and in clover u can change exaust, roof, and the rest.