Sounds like you're on the right track to me.
If you're going to get tubular upper arms Hotchkis makes the best ones for handling. They are a little harder to set up though, because they basically replace the forward mounting location, which removes the ability to adjust the caster/camber with the camber bolt in the front. They have to be set up using the heim only, which may take a few tries. I had to pull mine apart a few times before I got it where I wanted it. You still get the rear camber bolt to make adjustments, but it limits what you can do without adjusting the heim.
If you're on a budget, you can get Moog's offset control arm bushings and use them to dial in more positive caster and a little negative camber. Doesn't fix the other geometry issues like the Hotchkis UCA's do, but they're enough to get the alignment set up properly, and on a street car that's really all you need. Tubular UCA's are nice, and they'll flex less, but unless you really push the car you probably won't notice a huge difference as long as the alignment is set to more modern specs.
Torsion bars- do you have a big or small block car? Actually, 1.03" bars are a good choice either way, although if you've got a big block and really want it to handle on rails you might consider Firm Feel's 1.06" bars. I run 1.12" bars on my small block Challenger, but its STIFF on the street, not always a comfortable ride. Anything in the 1" to 1.03" range makes for a good ride, and with the Hotchkis sway bar up front to take care of any extra roll it will handle just fine.
Dr. Diff is the man. I would happily recommend anything he sells. On that point, I have a B-body rear and his relocation kit in my Challenger. Makes a TON of room in the back, I run 275/40/17's all the way around, and I could easily run much larger in the back. I believe that with the right offset you could get 305's back there. BUT, you should look into interference issues at the rear valance with the hotchkis springs and Dr. Diff's kit. If you have a dual exhaust that exits through the rear valance you may have to do some trimming of the valance to get things to fit. Seems like some people can run them without issues on the Challengers and other's have inference. Seems fairly minor though, check out this thread for more info...
http://www.cuda-challenger.com/cc/index.php?topic=80507.0I still run XHD's on the back of my Challenger with the offset kit. Dr. Diff sells front hangers that work with the longer springs, so you can keep the XHD's. When I got the XHD's the car had a pretty decent rake to it, not as high in the back as super stock springs but definitely higher than stock. Now that I've run the XHD's for awhile, they've sagged quite a bit. Gotta love Mexican made springs
. I'm guessing they're still a little taller than the Hotchkis springs would be, but not by much. And the Hotchkis springs will give better handling.
I would also be sure to include a rear swaybar and subframe connectors. Hotchkis springs are designed to be used with a rear sway bar, the springs are fairly soft so you need the sway bar to control the roll. And all of our cars should have subframe connectors. You don't necessarily need the ones made by Hotchkis, but you should have something. On that note, I have a set of e-body Mopar Performance subframe connectors I got in a package deal. I don't need them, so if you want them shoot me an email and maybe we can work something out. They aren't the strongest option out there, but you can bolt them in to locate them and then weld them in for added strength.
Rims and tires depend on a lot on what style you like and how performance oriented you want the car to be. 15" rims really limit the number of available performance tires and sizes that you can get. And no, BF Goodrich T/A's are not good handling tires for cornering ability, not compared to modern compounds and designs. If you step up to 17" rims, you'll have a lot wider range of performance tires and sizes available to you, as long as you don't mind the look of the larger rims. I run 17x9" rims front and rear with a 5" backspace. More than plenty of room with the B rear in the back, but pretty much the absolute largest you can go in the front. With the 275/40/17's I run I get some rubbing on the inside front passenger fender, I really need to roll the fender lip. No issues on the drivers side, guess I can thank Mopar's assembly line tolerances for that. But I also sit LOW in the front. Ideally, I think about 5.25" of backspace in the front with a 17x9 would be ideal, it would put it right on the frame at full lock but keep it off the fenders. But that's a big tire and rim, 17x8's with smaller tire, say something in a 255, would be a lot easier to fit.
