A friend of mine used bucket seats from a mid-size GM and the rear seat from a '64 Chevy Impala (the backrest had the speaker grille in it). The rear seat fit like a glove. All he had to change were the brackets that hold the seat back in place. He told me that any GM intermediate seat (like the '74 Olds seat noted in one reply) will fit fine in a '53. GM aparantly didn't do much in the way of changing the seats throughout the 50's and into the early 90's. Makes it easier for us.