I recently changed the oil in the 93 NC Fairlane V8..

I was turning it to tighten it up but it sort of kept turning...Seems the thread is sort of gone..

It still is pretty tight on but the next night I noticed a drop of oil at the bottom of the sump bolt...cleaned it up...

Next night there is another drop there..

How can I fix this? Washer?... I think the thread is gone so I dont know if it will help much..

Drain the oil out again.Get an appropriate tap to suit and retap the hole and replace the sump plug.
When fitting the new sump plug use an aluminium washer and also some thread tape on the thread or some sealant.And the do it up normally not too tight where you would swing off it and not too loose just little more than a nip.

The V8's used a plastic ( nylon ) sump plug washer. Just go to Repco or similar and get a new sump plug. The sump plugs are soft, and the thread in the sump are hard.
Don't over tighten it, it is a plug, it's not holding the crank in.
The original sump plug had a 7/8" head, and replacements usually have a 3/4" head. They have a 1/2" UNF thread.

I wouldnt use teflon thread tape on any part of the oil system in a car, if a bit of the tape get in the engine it will block the oil pump.

Yep dont uyse thread tape!

Get a tap, and re tap it out, get new plug from parts joint, use a bit of sealant on plug and whack it back in.

let sealant set for a while before putting oil back in engine.