I was reading the other day that DSM non AWS steering racks are also compatible. So, the width of the cars seem to be compatible. Most things are. Galant VR4 only bits are drive shaft, exhaust length, fuel tank, and I'm sure a few other things I've forgotten, or never knew about.
I was thinking early DSM drive shafts might have had different spline counts, so if you know what year your LSD rear came from, try and get drive shafts from that year. I'm sure the internet will fine tune results, but I was thinking the 4 bolt came out in 92.5, maybe..