Though I am still in the process of doing the same to my 59 impala, I plan to pain the inside first. My simple reason is if you paint the outside first it is harder to control the over spray when painting the inside. By painting the inside first (especially a different color) you can tape off all of the holes that enter the body when painting the outside. I plan to take off the doors and spray them seperate, so taping the enterior will be a little easier. write me back if i am off in left field and shouldn't be thinking this way.