As long as the pan is off replace the filter an ounce of prevention is always a good thing.
As for converter draining back it's just enough to be annoying when you put on the new filter.
I agree with fuel and timing.
I plugged my headphones into my laptop and listened.
It doesn't sound metallic enough to be heat riser.
Sounds more like spark knock.
Mine's the same.
I haven't done anything with it yet because I'm working on the rest of the car
first.
It did move in the other gear though.
Maybe some one here could shed a little light.
I was told it could be the low and reverse band.
Here's some picture of the shifter from my 68 Barracuda . It needs some clean up work but it might help out a bit. One of the pictures shows the u shaped bracket at the front of the shifter. It appears the set up didn't change much.
Hope this helps.