SFI has approved the use of sit on style crotch straps. They actually have a pdf document showing it.Any 6 point will require new bucket seats as the stock ones don't have a provision in the bottom cushion to pass the crotch straps (which by the way you should absolutely never sit on like I've seen some guys do ...).
In terms of harnesses, I always recommend Schroth, it's usually the pricier option but it's just better, and when it comes to safety, I'd rather spend a few extra $$ than spend my days in a hospital bed.
I did not have to do any kind of update with the magnaride software after installing the springs. I had been wondering if my car would still feel different from a true HP car, but after driving the track attack Mach 1's, I can verify that I noticed no difference whatsoever.@raidernixon I had a question about the springs and stabilizer bar. Did you have to do a magnaride software update after fitting the springs? and did the new springs lower the car any from the non hp? I'm trying to go with a set of apex wheels and run a square 19x11 setup with the vorshalg camber plates. I see you have just the rear sway bar listed on your build thread, how come you didn't go front and rear? Did you consider Steeda dual rate springs and bars?