That's why I'm liking this class it's mostly stock cars with some mods. Any preferred struts? And is it better to stick with 9" all around than a staggered setup?
For Autox, I would grab 9" (255 to 275) 200 TW tires all around, with lightweight wheels if it doesn't count as a modification. You will likely see your biggest improvement there. I currently run a staggered setup and am saving to go back to a square setup. Square has too many added benefits. Being able to rotate, only having to order one style of tire in case of a blowout, more likely to get deals for 4 of the same tire, etc.
If you are sticking with springs with struts and shocks outside, you need to get them rated accordingly. Your spring/shock will have a rating, you need to get springs within that rating. So until you decide what you want to run, I cannot tell you what shock/strut to run.
I personally have Bilstein in the rear and adjustable Koni up front, but I am also on coilovers all around.