1.Make sure you've installed CLEO4 or asi loader for SA.
2.Check the ID of the car you want to replace.You can find the ID in DATA/vehicles.ide.
3.Open the UpDownLigts.ini with notepad,change the number below [CAR_IDs] to the one you just found.
4.Put both asi and ini into your GTASA folder,and run the game.
5.If the asi doesn't work,just give up and replace ZR350 :p