This you needn't dilate, like DEFAUL in TXD already is SAPD

Pick out texture for what location car replace by, open TXD set (defaul=copcarvg.txd), advise 
by the help of programme TXD Wokrshop 3.5, and replace by choice texture BMP behind texture 
in TXD with title "whig_part", and save.

TXD Workshop 3,5 find on http://www.gtatools.com

TIP:
Take 3 or 4 copy files, this way replace by all variant and replace by behind all
police car in cities, and have you everywhere Honda Integra with by various location... ;)

DATA:
LSPD = Los Santos   = copcarla
SFPD = San Ferio    = copcarsf
LVPD = Las Venturas = copcarvg
SAPD = San Andreas  = for all, or directly for copcarru

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