Digikey appears to be out of stock of the op-amps, but the Electrical Components section on this site shows compatibility with one on Arrow, but I noticed it doesn't have the 2156 prefix to the part number.

Is this compatible with the circuit? https://www.arrow.com/en/products/lt1632in8pbf/analog-devices

 

You can completely disconnect the Inputs and the Outputs with Switches,
and the Op-Amps will just sit there and do nothing, idling.
But do not connect the Op-Amp-Outputs to anything other than
your Controller-Inputs, or just plain Air.
The Inputs can be left connected in any case,
this will save you the cost of one expensive 4-Pole, Double-Throw Switch.
I wouldn't worry about adding a Switch,
it would add more complexity, and points of potential failure, than the whole remainder of the Circuit.

You need to plan the Layout of every Part and Wire on Paper
before you start actually Soldering down Parts.

If you can afford it, Double-Up on everything in your DigiKey Order,
it might save you a week of waiting for a single additional part that got lost or trashed.

Hint:
When laying out Parts on your Proto-Board,
use a Single Strand of Wire from a piece of 22-gauge Stranded Hook-up Wire when
going from Point-to-Point on the bottom, "Pad-Side" of the Board,
then after you're happy with the way things look,
Solder the entire Single-Strand of wire to the Board along its full length, end-to-end,
jumping across each Solder Pad with Solder.
this creates a sort-of PCB-Trace made out of Solder, the Strand of Wire is just there as a guide.
Also, use your Resistor Leads as "Traces" on the Board in the same way as the Strand of Wire.

I've found using this technique is pretty-much Bullet-Proof.

You may have to get a Tiny-Pin-Drill set to enlarge the Holes for the Voltage-Regulator Pins,
they're kinda too fat to fit.

I forgot to give you a Part-Number for some Miniature Screw Terminals to attach In and Out Wires.
Here .......
DigiKey p/n- OSTYK22106030
Get-3.
Make sure you Color-Code them, or Label them some-how, so you'll know what goes where.
One whole side can be Inputs, and the other side Outputs, and the 3rd one is for your
Remote-Ride-Height-Control-Knob Cable.
( Use Ethernet Twisted-Pair Cable, you should have at least 3-pairs in that Cable,
use each Twisted-Pair as a single Conductor for your Remote Pot, it's harder to mix them up that way )
.
.
.

 

.
.
.
[/QUOTE]

Arrow is a Dollar cheaper, go for it, it's the Exact same Chip.
Don't forget to Down-Load the Data-Sheet,
it might be goblty-goop right now, but you can learn a ton of info by reading them.
.
.
.

 

Good point with the unnecessary points of failure, I'll look into finding an appropriate connector for the factory pins so that worst case, it would be just repining a few wires on the side of the road. I've definitely had to unmodify bigger tasks on the side of a highway before.

I already had several extras of everything in the cart, this stuff is pretty cheap!

I found a few programs online to aid in component layout, but I think just playing a little Tetris and wasting some paper once I have it all in hand will be doable.

I really appreciate your help in this. It will probably take a few weeks for delivery, build and install, but I'll report back with results when I have them.

 

Don't be surprised if you completely botch the first couple of tries,
I certainly did, only that was ~50 years ago.

It would still be a good idea for you to get Resistance Measurements from the Sensors,
and from the Controller-Inputs, while the are disconnected from each other, of course,
just to make sure there will be no Homer Simpson DOHH!!! surprises.
Don't forget to measure the Sensors from Ground to 5V, AND from Ground to the Output.
Mechanically Disconnect one end of the Sensor so a helper can move it up and down manually
while you watch your Meter, a super-cheap ANALOGUE Meter, with a real moving Indicator-Needle,
is the best tool for this step,
instead of a bunch of flashing numbers you can't read.

Another Tip .......
Put all of the Chip-Sockets in a straight line, that way, on the Copper-Side of the Board,
you can run 2- Power-Supply "Rails" right down the center of the Pins,
and pick-up all 6 Power-Connections in one tidy shot.
This is also good because the "Bypass-Capacitor",
( the Capacitor on the 5V-Output side of the Voltage-Regulator ),
needs to be connected as close as possible to the Chip-Power and Ground-Pins,
I normally put one one each end of the "Rails",
to reduce the remote possibility of some strange High-Frequency-Oscillation developing.
It just one of those "Best-Practices" type of things, this is not a critical application.
if it was, I would have specified proper Ceramic-Capacitors along with the Tantalums.
Keeping everything short and compact also contributes to Bullet-Proof-Chip-Stability.

Also carefully note that Tantalum-Capacitors are "Polarized" and should not have
reverse polarity Voltage applied to them, although, they will usually survive,
as long as it's substantially less than their Maximum-Rated-Voltage.
Check the Data-Sheet, or do a Google Search.
The Op-Amps will instantaneously release the DREADED-BLUE-SMOKE
if you apply Reversed-Voltage to them, even for an instant..
That's why you are using Chip-Sockets,
( Actually they're called by their "package" name of 8-Pin-PDIP, "Plastic-Dual-Inline-Package").
and not permanently Soldering the Chips in place.
That's so they're easy to replace if you accidentally Smoke one somehow,
it's also to keep the Chips out of harms-way, both Electrically, and Mechanically,
while all the other stuff gets Soldered-Up to the Board..
Also note that both the Chips and the Sockets have an orientation Notch,
so you won't put them in backwards.
.
.
.