HearMyTurboSpool

Hello Everyone! I am new to this fourm. So any help would be greatly appreciated. Soooo my question is... How exactly is narrowin and streching done? I recently bought the Revell 1971 Plymouth Hemi Cuda.. and would really like to make it in to a twin turbo Promod. But i am clueless on how to strech or narrow the car to make it Promod worthy. Any tips...advice..or pics would be greatly appreciated. Thanks in advance. -Greg