While GM columns are very similar, and almost identical in many respects, there can me minute differances in length and mounting hardware. I do know that a column from the same body type are generally interchagible, i.e. C-bodies such as deVilles and say an Olds 98, or even from C to B bodies. The swap from a C-body to an E-body such as your Eldorado may not line up perfectly.
The best thing to do is to place both columns side by side and inspect them and take measurements.
Mike
