Hey all, posting this info here because it is the most relevant spot I see, and I could not find the answer anywhere on the internets... so here it is for search purposes for anyone looking
The 4 bolts used on the lower ball joint are Toyota Part Number: 90105-10406, which have been replaced by 90080-10066. There are 4 required per side. These appear to be M10x1.25 bolts, 30mm long, though the stock bolt appears about 1mm longer than the 30mm bolt I bought. They are flanged head bolts, and I believe are supposed to be grade 10.9.
There are no numbers on the factory head, just a pattern of "Dot, dash, dash, dot, dash, dash" spaced evenly around head like the pattern you would see on an SAE grade 8 bolt, with the dashes aligned radially (from center out). Instead of the SAE grade 8 pattern of 6 lines, two of the dashes across from each other are a dot. I have no idea what this means, and I tried google'in it already.
Oh, and someone somewhere mentioned you should use blue loctite on the bolts because that is what the factory did... this seems like a good idea, I can't verify, but it is generally a good idea on any suspension parts anyway.
Out of 8 dealerships I called, none had the bolts available in stock. One had them at one point, but they were sent to a customer. No dealership is able to find the dimensions of the bolt if you were to opt for non-OEM replacements (local auto store/hardware store/etc). Disclaimer: Don't use non-OEM parts (figured I should mention, just because, but do what you want)
The below notes are from the Toyota FSM for a 1999 Toyota 4Runner 4WD, do not take my word for it, verify yourself if you are so inclined, this is for reference only...
- On-Vehicle lower balljoint inspection should show no more than 0.5mm play in vertical direction
- The 4 Bolts show torque spec of 59 ft-lbs
- Lower Ball-Joint Nut 105 ft-lbs
- Tie-Rod End Nut 67 ft-lbs
- Loosen but do not remove the 4 bolts until ball joint is popped loose, do not take nut off of BJ ball stud all the way until joint is popped loose, other wise stuff can separate violently...
- New BJ is supposed to be checked for turning torque before installation, this is how easy/hard it is to rotate the ball-stud in the joint, with LBJ ass'y in vise/clamp, rotate stud (using two nuts on stud?) for a continuous motion for 2-4 seconds, 4 times, on the 5th time, measure torque required to turn (on a beam style torque wrench, or super fancy digital readout one), it should be 0.8 - 21.7 in.·lbf according to the manual (.07-1.8 ft-lb)...
- Installation is the reverse of removal. The following is (not) copied from the FSM verbatim: If you broke stuff taking it apart, un-break or replace that stuff to put together, unless you can verify that a sufficient amount of zip-ties will do. Do not zip tie anything on your suspension together, no amount of zip-ties hold your BJ together if you forgot the nut or cotter pin, or if you forgot any of the 4 bolts. A zip-tie combined with a paper towel will however perform a satisfactory job fixing the gash on the top of your left index (finger) knuckle caused in removing the ball-joint.
One more edit: Be careful if you were to replace your LBJs with non-OEM from a parts store of you choice. The bolts I received with mine were 8.8 grade blackened steel instead of the goldish plating that the stock ones had. The replacements were also not flanged, and came with a lock-washer, with AND/OR without the lockwasher, they are 3-4 threads SHORTER than stock, and would likely NOT engage in the threaded holes of your knuckle enough. Make sure to verify your replacement bolt length, this is one of many spots that thread engagement is very important.
Thank you for reading if you got this far
Hopefully some of this info helps someone searching at some point