My 87 Lesabre has the basic gauge with just a speedo and gas gauge. I picked up a full gauge cluster with the tach and a few other gauges I want to put in my car. I know the oil pressure, temp etc probably won't work without installing sensors, but I would like the get the tach working. Has anyone swapped one of these in before?

What'* funny is that I am in the process of doing this very same swap in my 90 Park Ave.
Unless you are ready to switch pins around (and you will need the plug from the donor car to go with your new cluster since your current set up has the wrong kind of plugs), and you are good and figuring out what wire goes where both on the old set up as well as the new, I highly recommend either getting someone with experience to help you or trash the project. This isn't just a plug n play project.
I just went down to the wrecking yard today to get the plug. I still don't know if the new cluster will sit in the old dash or if I have to get another dash. Havent gotten that far yet.
From what I've read, you won't need to change sensors, which is a good thing.