Front Upper Control Arm

The Front Upper Control Arm (FUCA, sometimes called a Front Upper A-Arm, or Upper Link) is one of the major suspension components on the front of the Z32's suspension. It mounts to the chassis via a bracket, and extends outward to locate and help hold the main arm ("Third Link") of the wheel hub assembly.

A stock FUCA. Image unapologetically stolen from an eBay listing.

Location

FUCAs are located in the front wheel well, between the chassis of the car and the main spindle/hub assembly.

The FUCA's location on the Z32. It is labelled "Upper Link."

Stock vs Aftermarket

The FUCA controls the camber setting in the front suspension. As the stock suspension setup does not have any adjustments for this, upgrading to an adjustable aftermarket unit is very common.
There are two main types of aftermarket FUCAs, each with two different versions.

Stillen V1 FUCAs. These use silicone-injected urethane bushings with grease fittings. The adjustment mechanism is notorious for slipping and upsetting the alignment.	Stillen V2 FUCAs. These retain the bushings (and grease fittings) but now have more reliable threaded adjustment rods with lock nuts.
Midori-Style FUCAs (Pictured: Powertrix). Originally designed and introduced by Midori, these use bearings instead of bushings, and tightening collars to prevent the adjustment rods from slipping (which sometimes still slip).	Hybrid Style (Pictured: some eBay crap I actually have on my car). These combine Midori-style bearing mounts with Stillen V2-style locking adjustment rods.

A Note About Tension Rods

The factory FUCAs use bushings which allow a small amount of forward-backwards movement. This allows the tension rod to maintain caster. When installing FUCAs that use bearings (basically, any but Stillen) rather than bushings, you must install adjustable tension rods at the same time. This is because stock tension rods, without being of adjustable length, will put extreme lateral stress on the tension rods and ruin their bearings.

Cross-Compatibility

Z32 FUCAs are also compatible with R32s (Skylines) and vice-versa.