Pinging

[Pvmt-Pndr]

I have a 69 C60 with a 427TD, HEI distributor, block huggers and a custom 2-1/2" exhaust with an H-pipe I built .I just swapped the worn out governed Holley to a brand new edelbrock AVS2 650 cfm and took it for a quick 1 mile drive. It's pinging, I have the inital timing set at 8 degrees and currently not using vacuum advance though the HEI and new carb has provisions for it (I do plan to utilize it). At higher rpms she pings like crazy. It starts, idles, runs and shuts down perfectly. She seems low on power. The fastest I was able to get her up to was 42 mph. My gearing says I can go 59 mph in 5H at 3200 rpm. I'm confident my tach is not correct because it said I was at 3200 rpm at 42 mph. I've done a lot of googling but not too much specific comes to the tall deck. Any ideas?

It was pinging before I swapped the carb something terrible at high rpms and I haven't tuned the carb yet. It has a 2 speed rear end and I thought maybe my 42 mph was because I was stuck in low, not the case, it's definitely in high gear.