I was going to post the same ? They look like they would fit. They are the same size. If the E21 sliders will bolt on the bottom of the E30 seats then it's no problem. I currently have an old set of 5 series seats in my '82 320i. Even with the extra width they fit. They do hit the console if they are pulled way forward. I hope you get a response. I would like to make that same swap. Does anyone know if the E30 BMW front seats can fit in an E21 - has anyone got access to 2 types of seats out of the car to see if the subframes/bolt patterns are different? Are the seats physically wider? Anyone got any knowledge/experience of this?