When I did my rear springs, I used FJ62 rear springs on Rough Stuff mounts welded to the back of the original front mount. I flipped the rear mounts 180* and rewelded. I also removed about 6 inches from behind the wheel opening and added it back in the middle of the arch. Put the rear 40 springs...
I did a 2UZ vvti swap on an H55f, 285hp 325 lb-ft torque. It was an expensive swap but so FUN to drive!
With an LS you'd get as much power for a lot less money and still FUN to drive!
If I was to do it over, I might go with a diesel...