chassis
I agree with Brian here, don't waste your cash on a chassis dyno at this point for a timing issue. Like he said so much can be lost at the rear wheels you would never see the change in a few degrees of timing.
You may only gain 10 to 12 HP on a dyno with a timing change from 32 to 38 depending on the motor. I would start at 32 and work your way up, till the car slows down. Watch your plugs, and make sure you do every thing the same. Tire pressure, burn out, launch rpm, shift points, fill the fuel cell every pass.
The cost of building these motors any more $600.00 to put it on a dyno is nothing compared to what you learn about the motor on a dyno. Putting a pump gas 555 on the dyno in a few weeks. I' am hoping it will make 800 to 825 hp with a final C/R of 10.5