question: When it is warm outside (say 80's) and i have
the A/c on it tends to ping while under load is that
normal? It has fresh antifreeze and fresh oil the temp
gauge is in the center of the gauge.
I don't think is's normal. You have an '83 Datsun Pickup. I don't have specs for that engine, but many of those were 4 cy and the fuel mixer development was somewhere between a carbureator and multi-point injection. It may have had a throttle body injector.
In that era, pinging at low speed, say opening the throttle to something like 1/4 open at 30 mph, may be caused by an inoperative or plugged exhaust gas recirculation valve. The ignition advance curve was set with the expectation of having exhaust gas mixed with the intake and pinging can occur if this is missing.
This is a guess. There are other casues as well.
Fuel filter ?
Old cars with carbies don't seem to run all that well on the crappy fuel they have now with ethanol in it.