...has anyone just done away with the stock gauge clusters in favor of building your own more accurate cluster with Autometer gauges? I've been considering installing a Large tach and speedo in the existing cluster location and putting a bank of other gauges in the vast space available under the dash.

...has anyone ever done this, and are there any pics?

 

Try doing a search. There was just a post on it in the last week or 2.

And yes plenty of people have done it.