From the cowl foward yes they are the same with the exception of model specific trim. That trim will interchange as well but not be correct.
As far as rust repair goes for the rear section of the body depending on how bad you may be fabricating panels if you can't find them from the southwest. Convertible body panels are specific to the model on these cars. An Electra panel will be too long for a LeSabre for example. Most under car parts are the same except for driveshaft lengths.
I strongly recommend that you go to the reference section at the top of the page and view the 1961 service manual which will give you a better idea of the difference between models.