Does anyone know how much lower the transfer case crossmember is for the NP242 vs. the NP231? I am trying to get a skid plate, but my 231 has a dropped crossmember. Any other mounting differences?

Theres no difference in the mounting points or cross members between a 231 ans 242. The difference in skid plates is because the 242 is bigger. The section where the front drive comes off hangs lower.
Are you looking for a factory skid or an aftermarket skid? The factory skid that fits a 242 comes with a little step in it to clear the tcase. The 231 skid doesnt have the step but I think in later production years they just used the stepped skid for all applications. A factory skid can be used with a drop. Im not sure what aftermarket skids will work with a tcase drop and 242. Try the Warn skid. Thats what I have and it came with several spacers to be used with a drop or 242. If you need more spacers than they supply, Im sure they would send you more. I even have extras if they arent cooporative. Heres a link http://www.warn.com/truck/mounting-systems/body_armor_skid_plate_xj.shtml

Thanks, I was looking at a Rusty's, but will look at others. I think if the crossmember is the same, either one will work.