Bilstein 6112/5100 1999 4Runner Limited
 

I'm looking to order 6112 for the front or maybe 5100 all around. I did a search, but didn't come up with anything regarding 6112. Can you guys give me your opinions on what combo I should go with including springs. I plan to lift my 99 4Runner about 2in and use it for camping and moderate somewhat difficult trails. Also, what sites or vendors (If any) do you recommend?

There are several threads on here about the 6112s (and matched 5160 rears), I found them a couple years ago when doing the same research and posted info in a few of those threads. No clue on using the 5100s over the 5160's, I'm a "matched set" kinda guy.

You will not get 2" lift from the 6112s and a 1999 4runner (at least from its Stock height). You might get 1~1.25" depending on how much weight you have up front (plate bumper, winch, etc...) The lift figures are for the LOW 4runners, which are an inch or so lower than the '99.

Springs are 100% weight dependent. Figure out your weight (above stock), and then buy the spring from there. Just don't make the mistake of buying a spring weight for something you do 1% of the time, only to suffer the other 99%.

As for vendors, 4 wheel parts had the best pricing in 2019 when I ordered. Just do a little searching, there aren't that many places selling and pricing is pretty close. I was all-in at $1200 for 6112s, 5160, and ARB 2906 springs, shipped to my door.

From my experience with these Bilstein shocks on a 3rd Gen T4R, the 5100s are too tall for the rears and will actually bottom-out on themselves
with a loud crash on big bumps unless you go with their recommended Old Man 2" lift springs,
The Eibach Pro Lift 1" lift springs may be a better alternative. (See link)

With a 2" rear lift in place, the 6112s needs to be adjusted to level ride height. Right?
However, now you will discover that this all changes the geometry of your front end steering.
You now have bump-steer issues because the stock angles have changed.

You can lessen the effect by lowering the front to 4th clip, but it's still there and frame angle is slightly off.
The Eibach 1" lifts can help make better. PRO-LIFT-KIT Springs (Rear Springs Only) - TOYOTA 4Runner Base
My mechanic tells me that adjustable Upper Control Arms (UCA) will fix the Bump-steer problem for around $900.00 installed.

I suggest you go with stock height rear shocks and 6112s struts adjusted to stock height in front.
Verify with Bilstein that this height can be achieved.

I have 5100 tundra with about 3.5 lift in back. I'm going to replace with 4th gen 5160. You need extended bump stops and taller springs for those. I think 3rd gen 5160 will work for 2.5-3" with OME 890 with stock bump stop. I only got these 5100 because 5160 were out of stock and I had blown one of the rears and needed something quick.

Forgot to say I have 3rd gen 6112 in front, which gave me about 2.75 for some reason. It can be very bouncy going slow but rides great at speed, like bombing down dirt roads or on the interstate. Very flat driving. It can go straight over pot holes and speed bumps (in an building development with no houses or anything yet) at 50mph no prob (with E-rated KO2s). The progressive valves or whatever I suppose. I don't like the boat-like feel of soft shocks, I drive my 4runner like a go-cart most of the time tbh.

If you can find bilsteins 5100 or 6112 and 5160 in stock as a set please post it. Because every where I've looked they are back ordered.

Is there a part number for just the 6112 shock without the spring? Everywhere I’ve looked it’s a combo.

Only comes with a spring

You're not going to improve on the unit by using a different spring. If you're running some giant plate bumper and winch combo and need a heavier spring, use the Tundra 6112. Not only will you get the heavier spring, but the VALVING in the shock to compliment that spring.