Trailing arm adjustment

[Pondscum]

I've been searching and have not been able to find a definitive answer on whether to raise or lower my trailing arms. The truck is a 67 c10 swb, it has a 454 iron headed and th400 with bout 3000 stall. I'm getting ready to put a set of 305/60/15 M/T drag radials on the truck. Weight of the truck is 4080 lbs without me in it. I'm running a 2 inch lowering block in the back at the the moment and lowering the arms would help my pinion angle. I would just like to know to lower or raise the mount so I can get better traction and not just spin. Anybody still running trailing arms at the strip your opinion is valued, thanks for your time.