i dont know for sure, but here are some things you'll want to consider:
If im not mistaken, the inlets and outlers on the mufflers used with the magnaflow c/b are caddy-corner from one another. the magnapcks are straight through, meaning the inlet/outlet line-up. this could be an issue when trying to get the packs to fit right up. if it is a problem, a competent exhaust shop should be able to work it.
im considering the same thing, only i have the SLP LM, which uses straight through resonators similar to the packs. i doubt my current tubing will be a perfect fit for the packs, but it should be easier than converting from mufflers.
anyway, the part number for the PACKS themselves is : 14416. Shop around, you can find a pretty good deal on them. I've found them for as low as $53 each. good luck
I'd have to agree about alignment issues. I asked this very same question awhile back and the majority of the responses were "no they won't be an even swap out." You'll have to have some customizing done to get them to fit correctly. Any good exhaust shop should be able to do that for you, if you can't do it for yourself.
to add to that, as fas as i know most custom exhaust shops use aluminum. im pretty sure magnaflow uses stainless steel. i dont know if that matters to you or not, or if would even be an issue.
One other thing is that the tubing coming out the muffler curves on its way out, to meet up with the next pipe. On the standard system, its straight out.