Mustangs Unlimited probably has a similar set for a few bucks cheaper. I've had good luck on all their stuff. I think their kit has KYB shocks which are what I have and what are highly recommended. I like them, so check them out. As far as the questions, you shouldn't need to replace the arms if they were recently replaced and you are only using it for street. I put the 620 coil springs on mine and the ride height stayed the same, but the handling improve dramatically with a lot less body roll, but ride is still comfortable. 45 year old front springs softened so much that the shorter, stiffer springs didn't lower the front. If you use stiffer rear leaf spring, look at going to a mideye or reverse eye spring. I used the regular 4 leaf and it raised the rear end 2 inches, because the old ones were sagging so badly. I put lowering blocks in the rear to bring it back down. Everything is a simple bolt in and out, but the front bolt on the rear leaf springs are usually rusted in pretty good. I had to use and air hammer/chisel to wedge the bolt out. A lot of guys have to cut it out. Good Luck.