I just joined this forum but I wanted to report that I've just successfully swapped in a very low mileage FRS LSD diff into my automatic 2004 IS300 that came with an open diff. I used the FRS bolts to mount the diff in the front and I used the IS300 bolts to mount the diff to the rear crossmember. At the same time I upgraded to FIGS rear diff mounts. I haven't noticed any odd noises or other issues. It essentially bolted right up. I have noticed that with the gear ratio change to 4.10 the pickup from a stop is a bit improved. For the install I only removed the rear sway bar. I didn't remove the exhaust at all and I simply unbolted the axles from the diff cups and the driftshaft bolts from the front of the diff and dropped the diff right out. I swapped the diff cups onto the FRS diff and my buddy and i put the new diff in without much trouble. I will say that it took us about 8 hours over 2 days to do this in my garage without any air tools or lift. I had the rear of the car lifted on drive up ramps and that was it.