I took apart most of my 1989 4Runner a few years ago. I'm just now getting parts de-rusted, primed and painted.
Can someone tell me the correct location where this part (there is a Left and Right part) goes? Thanks.

 

I cannot figure it out, but my advice is to check out the parts diagrams at toyodiy.com to see if anything looks right. I did some looking and cannot seem to find a match. You might also find it if you look at enough pictures of 4Runners on bring a trailer. Lots of listings there have very detailed pictures that might show something.

I am assuming your truck is an '84-'89 body style, not a late '89 that could have been sold as a '90? Are the any numbers on the back side of it? Do you know roughly what area of the truck it is from (exterior, interior, engine compartment, etc.)? If it could be from the engine compartment, is yours a 22RE or 3.0?

 

I have a 1st gen 89 3.0. I thought maybe it came from the front end somewhere. I went thru many threads about build ups and restorations and didn't see any resemblances.
They are stamped L and R. No part numbers. Thanks for the website link.

 

I'm not familiar with that particular part, so I don't know what it actually does, but I'm gonna guess it's this:
52133-89109
BRACKET ASSY, FRONT BUMPER SIDE MOUNTING, RH

It only appears on the 8/1987 to 3/1989 front bumper & bumper stay parts diagrams.

In other words, there's also a 8/1983-8/1986 and a 8/1986-8/1987 version of that front bumper parts diagram, and they don't show those brackets or anything substituted in place, so seems like something that got added later in production.

Link to PartSouq parts diagram for a VZN61 (1st gen V6 4Runner)