Pinging...still haven't figured it out

[Rooster's82]

So a couple of weeks ago i started a thread about my engine pinging when i didn't use premium gas and got a lot of good advice...I applied most of it but the engine still pings. (it actually started pinging with premium too)

First, I had the timing checked and set to specs.

I figured out my vacuum advance and corrected it. There are no leaks.

I ran some SeaFoam directly into my engine using a vacuum line. I was told that carbon build up will "glow" and cause pre-ignition. I think i did a pretty good job...but i think i could do it again.

I put in a new 180 degree t-stat, and did a very good flush, now the coolent is nice and green with no rust, there are no leaks. It calls for a 195 but because the engine pings worse at higher temp i thought a cooler t-stat might help. Funny thing is the engine runs at 195-200 now, why i don't know.

I also got the carb dialed in better, and gave her an oil change with 20W50 oil.

End result...

I have been running regular gas and it runs great until it gets to 195-200 then during mild acceleration it pings. regular cruzing speed NP...heavy acceleration NP.

I have not tried premium fuel yet but i have a feeling it would mask the problem...but don't know for sure.

When it pings the engine heats up like crazy (210-220 in a matter of seconds) and the pinging gets worse. I can drive the truck and prevent it from pinging...but i have to lay into it to do any type of acceleration.

Also at idle the temp starts to creep up. Which doesn't make sense...i have an electric fan that pulls way more air at idle then the stock fan ever did.

The previous owner dented the headers in 2 spots in order to get to the spark plugs....could this be causing enough restriction to heat up the engine and cause the pinging?

I should also add that previous to doing everything above if i put regular gas in the truck was nearly undrivable....now i can run it pretty well with regular...Basically i have made VAST improvements...but haven't quite eliminated the problem yet.

HELP...I don't know what else to do!