Good looking car. No problem with the 400 bolting up. You probably will be better off with the 400. Depending on the year of the 455 block some will drop right in and some years need adapters for the motor mounts.. Interesting, I thought there was some issue on the door hinges between 7 and 8. 3 mounting bolts on the 7 and 4 on the 8. Apparently they do bolt up.