The mopar offset kit is designed to work with SS or oval track springs only, not the stock or XHD springs. I believe Dr Diff has an offset kit that allows you to keep the stock or XHD springs in the relocated position.
SS springs do have a lot of arch, but with the multi position hanger and a smaller lowering block, you can put the ride height exactly where you want it. They are a big firm, but if you have lots of power, they will plant it very well. You can always remove leafs from the pack to lighten it up if the ride is really offensive.
XHD will fit in all the stock locations and do a decent job of controlling moderate power. They ride very well.
A third option , if retaining stock mounting locations is important to you, is to use the original main leaf, but add the SS pack leafs underneath it. This allows you to keep stock parts with the SS control.
If you want to do the B body conversion at the same time, I'd recommend the SS springs. Once you get the springs, you'll notice they are massive compared to the stockers. Like I mentioned above, you can remove 2-3 leafs from teh pack to lighten them up some.
