I just love reading about guys that buy a GT and then start putting Dark Horse parts on it, because the GT is better than a Dark Horse. I have yet to see anyone putting GT parts an a Dark Horse.
Thick spacer change the load on the wheel bearing and can cause premature bearing failure. I am confident that others won't agree with me, but I am telling what I was told several years ago when I had spacers on a vehicle and one of the bearings failed.
I put an OPTIMA Battery in mine and made sure that I attached the vent and plugged the other vent hole. Should not be an issue if you don't use the tube because the S550 battery is in the same spot and doesn't have a vent. As a side note, an S650 battery tray will fit in an S550 with some minor...
You haven't seen my car, you don't know the body shop but you assume the work is not done correctly because the body shop i have used, by coincidence is a preferred State Farm facility. This is why I don't take forum recommendations.
My S550 is lowered and I have 20x10 with 285/35 tires. No issues that I have experienced in 9 years. My S650 Dark Horse and my S5550 GT/CS are the same basic architecture, so they should fit the same.
I have State Farm and the body shop I wanted to use was a State Farm approved shop, so I just dropped off the car and they covered it. Didn’t need to get an estimate. Side note, the repair work was outstanding and painless.