The MII crossmember can be notched. It's actually overbuilt to begin with. If you plan on using a sway bar, you would need to use a front mount one, instead of the rear mount that most MII's use. If you're worried about strength, You can always add and extra gusset.
Most of the MII manufacturers can do a custom crossmember that moves everything down for more clearance. A phone call or two can give you the intel you need. Then there's the universal kit that you cut and notch yourself...
