Hi.
Fully rebuilt the 3.8 v6 in our 86 convertible three years ago and only use it occasionally- last couple of time noticed that the coolant temp has risen from where it always used to sit.
The only changes from the status quo recently have been...
Recently- I noticed that the distributor was loose and moving around reasonably freely, so bolted it down where the idle sounded best. I have also replaced the serpentine fan-belt because the old one squealed a lot especially in damp weather...

1986 3.8 v6- engine temperature rising