I don't think I could go low enough to make it worth your while since this is geared 4.30 you'd have to regear this differential to get a ratio that is available for your front end too. You are probably best off getting a 4.10 ratio since you could use the OEM front diff from a 4cyl 2005+ Tacoma in your 4runner.
I have considered the 4.10 dirrection but I am keeping my options open. ECGS offers 4.30 gears for the front clamshell in 4th gen 4runners so I could run the 4.30 3rd in the rear no problem.