Hey, just made an interesting discovery. Not sure if it has been posted here before. I am under my Burb, swapping out engine mounts. Picked up new clamshells at Checker for 4x4. Took off the old mounts and they are flat bottom, 2wd. Well, guess what. The 4x4 mounts don't fit. The bolt holes in the frame brackets (bottom center) are way off (too long and not in the center). So, I am fuming. Well, call up the Chevy dealer and beg for some insite and he informes me that from 87 to 91 SUBURBANS, the engine mounts are the same for both 2wd and 4wd. Not sure of K5's but he definately said that they are the same for the Burb. He knew EXACTLY what and why I was asking that question. I can post a few pics if anyone is interested. BTW, do yourself a favor and CHECK YOUR ENGINE MOUNTS. Mine were metal on metal and the rubber was wasted.