What RPM going through the traps with a 408?

I'd check timing, fuel pump (the car might have a slight stumble that would cost you some time, higher volume pump) and run new 28" slicks. You could be spining the slicks on the rims.. Sounds weird but you can do it. You could try to drill and tap screws into the rims and slicks to prevent the rims spinning in the tires. The screws are found at most performance shops (summit) I used some (moroso) on a duster with widened rallie wheels and they worked great and the car hooked up alot better. I used the painted stripe idea on the tires and was amazed how much the rims spun inside the tires before I had screws in them. Hot rod Magazine had a writeup about this idea. Timing and maybe rejet the carb? I think you have air shocks in the rear, adjust the pressure to put more weight on the rear of the car...might help to pop those front wheels up...good luck