Problems running at operating temperature

[hatzie]

Sounds like spark knock otherwise known as detonation. It could be extreme piston slap but let's think good thoughts.
Check your base timing to be sure it's proper. The steps to do this are in the service manuals.

Carbon buildup on the piston crowns and head chambers will increase the compression ratio. The old fashioned remedy was an Italian tuneup. If you've never heard the phrase "Italian tune up" before, basically, it means driving your rig hard and bringing it to near the redline for a several mile stretch on the highway with the goal of knocking loose carbon deposits.

The other option is water but you want to be extremely excessively careful to not hydrolock the engine.
http://youtu.be/KFtp_jmLF3k

Assuming the base timing is spot on another thing to try would be bumping up the octane one tier to 89 on your next fillup. If you have a half to a full tank you might try a bottle of octane booster. I wouldn't use octane in a bottle as a regular thing but for this kind of condition it may let you use up the lower octane fuel without an excessive amount of spark knock.

I've forgotten whether Texas allows the sale of 86 octane fuel. Last time I was in Dallas was in 2010.
If you have 86 octane in the tank that is most assuredly your problem. Just say no to 86 octane in your post 1960 GM V8.
Old crappy fuel has lost some octane too.

[LT7A]

Glad to hear that it runs now. Hopefully you can sort out the pinging too.

[kevinc]

The EGR valve is good. It holds vacuum and the engine stumbles when I push up on the diaphragm. The coil and ignition module is new as of a couple months ago. Since code 43 is related to knock sensor I may as well replace the knock sensor.