Your '88 240 should be close enough to my '91 240 because I got my parts from an '88 240.

I went to the bone yard and found a wreck with a tach and a little clock over to the right where your car has a blank plate.

On the wreck, pull off the trim around the clock, (save), slide the clock straight out unplug the wires and follow them to the back of the tach and unplug them from the tach, save these wires, and save the three little rubber gizmos that held the clock still. On the back of the tach you will see one white with red stripe wire, thats the signal wire. Study where it comes from your car will have that same wire buried somewhere in the harness, mine was tough to find, but it was there.

The tach then unbolts with three little bolts, then pull it straight out.

There are several electrical contacts that are there so kind of walk it out.

I suggest pulling the bone yard one first. I think I was charged $5.

I also got an extra clock trim and rubber gizmos and put a oil pressure gauge below the clock, those holes behide the blank filler panels seem to fit all standard (3"?) gauges. In all the job was under an hour to install.

Steve M.