I did the same thing to my 59. Sandblast is the best way to go. I however applied Zero Rust. After sitting out in the elements for a year, now two years later and still looks great!
Two pictures of my frame before and during.

http://home.comcast.net/~bklyn611/wsb/html/view.cgi-photo.html--SiteID-299364.html

http://home.comcast.net/~bklyn611/wsb/html/view.cgi-photo.html--SiteID-299363.html

rebuild not replace