I would still double-check the cluster grounds. Some clusters have multiple grounds, as some clusters have two circuit boards (left side, right side).

So if the Ammeter and Oil light work, but the fuel, temp and turn signals do not, I suggest checking that side. It never hurts to have more grounds than necessary.

Also, if things work fine when the lights are off, and things go screwy when lights are on, that is also an indication of a poor ground. Basically, you're overloading whatever ground circuit is still functioning, due to resistance, corrosion, etc.

I still say, check grounds on the cluster. Add one or two new ones just in case. All the clusters in all my cars work.