No traction

[C10Blackout]

So I got my 71 c10 back up and running. We had a nice day out at the local drag strip, so I figured I would take it out for a couple passes.

The truck is a LWB lowered 4 inches in the back and 3.5 in the front with drop spindles. Nothing overly special about the motor. 355, mild can, stock heads, air gap intake. 2400 stall on a th350 trans. If my math is right it has 3.08 rear gears. Nitto NT555r's on 18psi(10.5ish inches wide)

Well I know posi is going to be my next course of action cuz my rear driver tire smoked down the track, but in the mean time I figured I would get some advice. I went a 15.9 smoking the tires all the way down the first pass. Rolled in the 2nd pass instead of launching and went a 15.6. And the final pass I launched and attempted to feather and still only could pull a 15.6 again.

What can I do to get better traction? I have an anti squat kit in the garage that I haven't had time to put on the truck(came with it), but I think that will only help so much. Just looking for some advice. Not trying to spend crazy amounts of money, but something I can build towards. I'm not looking for 9's in the quarter, but I'm not trying to be slow either.