It's not bad at all to fit the taco bumper on a 4runner, you just need to cut the plates on the ends of your frame off (very easy, they'll just fall off once you grind the welds). The ARB mounting brackets then slide over your frame rails and are bolted on. Then the bumper is bolted to the mounts. This all you NEED to do.
However, after I bolted the brackets on, I strengthened them for winching by welding the brackets to the frame (in spots that would be easy to grind off if I ever wanted to remove the bumper). I've done a lot of pulling on my bumper and have had no problems with my method.
There is also another mod to consider though, in which you can weld some angle iron inside the frame and then put a bolt through the angle iron and the bracket for added pulling strength. L@@K:
Frame Endcap Mod for Winch Bumpers | Northwest Toys
(this is above and beyond what ARB designed for the Tacoma or the 4runner, but was developed by off-roaders who do a lot of winching)
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2021 Tacoma 4x4 TRD Off Road Double Cab Short Bed (my DD)
2017 4Runner 4x4 Limited (the wife’s)