Since you are running bias ply slicks, I would experiment and try letting the clutch out as fast as your leg will work. Adjust tire pressure / shocks and Launch RPM to get about 1 - 3 tire revolutions before the tires stop spinning.

That keeps the engine from bogging, and results in very good (not best) 60' times and tends not to break anything. This is what a lot of us street car guys do. Unless you run a specific slipper type of clutch, I wouldn't be letting the clutch out slowly, you'll just wear it out quick.

On the top end, look for fuel delivery. I had just run 120mph and the next two runs were around 113mph. Based on my LM-1 going lean in 3rd and 4th gear, I found out that the fuel pump / regulator were going away and not delivering enough fuel and causing it to go way lean on the top end.