Dear Gaurav, for a career in Car Designing, you should ideally pursue B.Tech in Automotive Design. And an internship with automobile industry is mandate. You need a very strong portfolio of 2D and 3D drawings and art pieces for placements. You should have a very strong professional portfolio to be hired by he best companies including Tata Motors. There is a Dual Degree Programme in Automotive Design with B.Tech in  Engineering Design and M.Tech in Automotive Engineering. It is a 5 year course offered by IIT Madras. While we cannot point out which step leads you to a job in Tata Motors, this integrated programme for IIT Madras has placement recruiters from Tata Motors among many other companies.