Heidts Pro-G IRS Base Kit IRC-800 — 1974-1981 Camaro & Firebird

Heidts Pro-G IRS Base Kit — IRC-800

The Heidts Pro-G IRS replaces a live rear axle with a true independent rear suspension, built around tubular control arms, steel outer uprights, a top crossmember and billet aluminum single-adjustable coilovers. The upper link geometry generates roughly half a degree of negative camber gain at three-quarter bump, which is what keeps the tyre flat under cornering load.

IRC-800 is the base kit. Read the next section before ordering — what it excludes matters more than what it includes.

What the Heidts Pro-G IRS Kit Includes — and Excludes

This part number supplies the suspension structure only. It does not include a differential, axle shafts, or brakes.

Included: aluminum centre-section housing cut for a Ford 9-inch third member, tubular upper and lower control arms in steel, steel outer uprights, top crossmember, frame mounting brackets, single-adjustable billet coilover shocks with springs, polyurethane bushings, and a 0.875″ (22mm) sway bar.

Not included: the Ford 9-inch third member itself, CV half-shaft axles, brake rotors, and brake calipers.

The distinction on the third member catches people out. The Heidts Pro-G IRS base kit gives you the aluminum housing designed to accept a Ford 9-inch centre section — the gears and carrier are a separate purchase. Source one from our differential and rear-end components range, or see the Ford 9-inch posi third member.

For the brake side, browse brake systems — the Wilwood AERO4 rear brake kit is the common pairing on this style of build.

Specify Your Spring Rate When You Order

Coilover spring rate is not a default on the Heidts Pro-G IRS — it has to be chosen for your car’s corner weight, intended use, and ride height. A rate suited to an autocross car will ride harshly on the street, and a street rate will roll under competition loads.

For best results: have your finished corner weights, or a realistic estimate, before ordering. Add your spring rate to the order notes at checkout, or send it with a quote request and we will confirm it against the build before the order goes to Heidts.

Why Independent Rear Suspension

The Heidts Pro-G IRS exists to solve one problem. A live axle ties both rear wheels together. Hit a bump on one side mid-corner and both tyres are disturbed, which is the handling ceiling on nearly every classic muscle car chassis.

The Heidts Pro-G IRS lets each wheel move on its own. The result is more consistent contact patch over broken surfaces, less unsprung weight, and traction that holds up when the power goes down. On a high-horsepower build that is the difference between putting the power to the road and spinning it away.

The single-adjustable coilovers let you tune damping after installation rather than committing at purchase — worth having when the same car sees both street miles and track days.

Fitment — Confirm Before Ordering

Heidts Pro-G IRS kits are chassis-specific. Part number IRC-800 is understood to be the base kit for 1974–1981 Camaro and Firebird, but confirm this against your exact year and body before committing — track width and mounting differ across the range, and this is not a part you can adapt after delivery.

Run a compatibility check, or book a technical consultation if you are unsure. If your chassis is not covered by IRC-800, send a part request and we will source the correct Heidts Pro-G IRS part number.

Installation and Support

Fitting a Heidts Pro-G IRS is a structural chassis modification. Subframe connectors are strongly recommended, and forward struts locate the assembly under hard acceleration. Installation should be carried out by a fabricator or shop experienced with chassis work.

See our installation guides, or let us handle the whole build through custom builds. Manufacturer documentation is published by Heidts. Review warranty information and shipping information — this kit ships freight, and lead times apply on made-to-order configurations. Browse more suspension components.