Need some advice..Panhard, etc..

I currently have double diamond 3 point SFC's, Bilstein hd shocks on stock springs, boxed lower control arms and that is about it for suspension upgrades. Over the past few months I feel like the rear end is a little looser than it was before. I have made 200+ passes down the 1/4 mile track and was thinking about more upgrades. So here is what I am wanting and need advice. Car only runs mid 12's with minor mods and is only about 350 rwhp.
1)Panhard bar - adjustable or not? I have no plans on lowering the car.
2)adjustable lower control arms? or just keep the boxed ones I have.
3)TQ arm? Adjustable or not...or do I need one and if so, which type.
4)Anything else I may be missing.
Thanks in advance for any help. I am not racing now as much as before, so it is mainly for street use and to solid up the rear end better. Car feels like there is slightly more play in the driveshaft too...not sure if that can be corrected with a tq arm or not. I don't have a ton to spend, but want to do it right. The control arms where bought from a person who used to make them on here and once a weld broke and was fixed where the bushing is. I was thinking about getting new ones for this reason and I opted for stock type bushings so they would be quiet(was when I first bought the car) or I would have went with the energy suspension ones if I know what I do now.

1) even in stock height form, the rear isn't perfectly centered left/right under the car.
2) adjustable trailing arms allow you to center the rear inside the fenderwells and correct thrust angle. which is the rear pointed left/right of straight ahead.
3) adjustable, so you can fix pinion angle with it.
4) relocation brackets for the trailing arms.

play in the driveshaft cannot be fixed with a torque arm. when you say car feels like it has play in the driveshaft, what are you feeling? have you gotten under the car and checked the u-joints?

The Play I am feeling could just be from the 3400 stall converter and is mainly letting off the gas and at certain rpms. I went to the track Sat and was cutting 1.695 - 1.701 60 foot and was happy that at least the 60 foot times were ok, now maybe I can drop the times a little more with some more suspension mods.