What level do you have to be in san Andreas to customize cars?
To customize cars you have to have completed the mission Cesar Vialpando; the mission where you have to customize a low-rider and then compete in a low rider competition.
These are the TransFender auto custom shops to be found around San Andreas. Their locations can be found as follows: 1. In Los Santos - next to the Pay 'n' Spray shop in the Temple area. 2. In San Fierro - the rear of Wang Cars, across the road from CJ's safehouse garage. 3. In Las Venturas - the east end of the Come A Lot casino.