81220-YY020 doesn't fit
OK, I picked up a $30 pair of Rav4 fogs lights (part number in title) and they didn't fit.
The fog lights on the 2011 trail edition are held in by one screw thru the top outside tab, the bottom outside tab is unused, and the two inside tabs simply slide into pockets in the bumper housing. The location of each tab on the Rav4 light housing is about 2.5mm different from the 4Runner part, enough that if I index off the one screw and trim all the other tabs the light will be noticeably off center in the bumper housing. All the other important dimensions are pretty much spot on, so from a manufacturing/inventory perspective it seems like an odd choice by Toyota but it is what it is.
If I run across any equally cheap LED lights with the actual 4Runner part number I may give it another shot - in the meantime I'll just get some LED replacement bulbs for a little better output.
Thanks for all the suggestions.