Now that you have stringed your chassis you can look at the tire age? If these tires were used one year and than were frozen over winter you can not expect them to be very aggressive. The curing process of your tires never sleeps. If I were in your position I would be looking at D1 goodyears with stiff side walls for your car.
As for the shocks, you are muddying up the water by adjusting the shocks independent of each other. They will be the same on both sides when you work out the other problems you may be tuning around.
What you are seeing at the track getting 1.17 60' indicate that you dam sure are working the track well,even with the spinning problem.
Ladder bars will require a lower setting as power increases in the same chassis. Having said that, You may need a lower hole than you have available in your chassis bracket and may not be able to adjust to maintain an appropriate pinion angle if you were to place the rod end low enough for your power level. You have a short car and a short instant center due to the suspension choice being ladder bar no doubt 32" long. I would like to see the ladder bar at ride height run down hill at least 5 degrees for starters. This will give you more traction 10' into the run and down track.
If you tighten the shock's rebound and this helps traction, your car will prefer a lower ladder bar mount than what you are using. If the car responds positively to loosing the top or rebound of your shock your car will possibly like a higher ladder bar setting.
As for the springs, what rate are they? 110# or less? If so you may try 130# ones to slow the hit and help prevent over planting of the tire's. This will help some if the instant center can not be lowered enough for your set up.