That is the same subframe I used on my project. It is a GM G-body which includes 78-84(?) regal, monte carlo, grand prix, malibu, el camino, cutlass etc. The parts are all interchangeable with a few exceptions such as the spindles. rotors, bearings from 78 are not the same as the later years. Why I do not know.
You can see my installation in my picture trail album or in my gallery pics.
If you have any questions let me know.