All the ground wires should be clean and tight. The Isolated Ground Junction Block, shown in the photo below is where ground wires originate for the electronics in the Reatta. It is very important for them to be clean and tight to prevent problems with the CRT, IPC and other electronic devices. I have found the ground terminals to be slightly loose on several cars, especially the one (on left of picture) that attaches to the radiator support.
There are also ground wires connected to a stud located behind the belt tensioner as shown in the photo below.
Thanks to ChrisWhewell for providing this photo
Thanks to Barney Eaton, member of the AACA Reatta forum, for this information.