Murf is correct. The LS engine family runs hotter than the 1FZ-FE, and when you stuff it in the engine bay, you fowl up the airflow. You will have to take some good steps to keep it cool. The very first thing to ask yourself is "Why do an LS swap?" If you just want a V8 LC, then a 100 or 200 series might be better. I just drove a 200 today and that thing flys! For me, I had a 100 before sold it, and wanted an 80. My 80 unfortunately had a motor that went south on the drive home from picking it up. I was looking at $5k+ for a full rebuild, so for me it was a matter of spend that, or go a bit more and have some fun with a swap. At this point in time, I can say whole heartedly that it was worth it. Would I do it all over again.........not so sure on that one. It is NOT an easy swap. It is NOT a cheap swap. I am at around $9k on engine, XMSN, adapter, harness, and misc, and I am not done. I am still smoothing out the cooling challenge.
In the end, you need to figure out what you want out of it. I wanted an 80 series with lockers, and more power. I have no plans to sell my rig, so for me, it is worth the time, money, and effort to do the swap. It will white smoke the tires, and run 75 up hill, but it was also 11 months of weekends in the garage and it is still only 95% done. There is a reason Slee, TLC, PRC, and others charge so much for the swap.......
Hope that helps. Reach out if you have questions.