They apply factory graphics hours after painting vehicles.
Two local body shops have me do replacement
sign work for them.....I'm usually called in for installation the day after they paint, usually installing while they reassemble the vehicle.
Put hood stripes on my Jeep the day after it was painted, no problem and came off just fine four years later.
Ask the body shop guy what he thinks. Paint has come a long way since the days of waiting six months to letter on it.
Mike is right, though. Let your client make the call. They'll almost always tell you to go ahead and do it anyway but at least you'll be able to say to explained it to them if there ever is a problem.