60' at 1.64 should be in the 7.4x range 1/8th mile. 330' around 4.75. 1/8 mile MPH should be ~91ish.
Are the calverts the loosest shock? If so, the car appears to leave better with a looser shocks. The numbers don't lie! I wouldn't mess with limiters, IMO, you aren't in that neighborhood. Have you altered the upper a arm bump stops?
Something in the driveline is chewing up HP is my guess. Looks as if it gets softer further down track. First on my hit list would be converter, Second fuel delivery. That thing could possibly take a ton of timing, maybe 40-44 total with that large cam, open chambers and low compression. Should have a LOT of initial/idle timing, 20-26.