Iam renovating a 69 Fastback. Factory included an 8" 2.79 Rearend. Iam wondering what the out-to-out length is on the rearend, and if a late 80's, early 90's GT disc rearend could be easily installed. I know that plates would need to be welded on to allow for the leaf springs. Except for that, any other unforseen items???