Upgrade your classic Mustang’s rear suspension with QA1’s complete 4-link system, featuring a custom QA1 9” rear housing. Designed specifically for 1964–1966 Mustangs, this all-in-one solution delivers modern handling, improved traction, and the strength to handle serious power. Whether you’re building a street-driven restomod or a pro-touring performer, this kit is built to transform how your Mustang drives and feels. MODERN HANDLING, CLASSIC FIT QA1’s triangulated 4-link replaces the factory leaf springs with a fully adjustable, geometry-correct rear suspension system. It dramatically improves traction, cornering, and ride quality by eliminating axle wrap and maintaining consistent pinion angle under load. The included QA1 9” rear housing ensures a perfect fit and the durability needed for today’s performance builds. SINGLE ADJUSTABLE COILOVERS This kit includes QA1’s single adjustable shocks, offering 18 clicks of combined rebound and compression adjustment. With one knob, you can easily fine-tune ride comfort and performance for your preferred driving style - from smooth street cruising to spirited cornering. STRONG, RELIABLE, AND READY FOR POWER The included QA1 9” housing features fully formed trailing arm brackets, a fabricated steel center section, and heavy-duty 3” OD axle tubes. Together, they create a rigid foundation capable of handling up to 800 horsepower. Matched 31-spline alloy axles ensure strength and smooth operation mile after mile. RIDE HEIGHT & ADJUSTABILITY Easily dial in your stance with adjustable ride height from factory level to 3” lower. This flexibility lets you fine-tune your Mustang’s appearance and performance without compromising geometry or drivability. EASY INSTALLATION This kit comes complete with everything you need for a straightforward installation - from the housing and brackets to shocks and hardware.
FITMENT NOTES: Fits 1964–1966 Ford Mustangs: Designed to work exclusively with the included QA1 9" housing: Weld-in installation required: Factory wheel mounting surface: 57 3/8": Compatible with Big Ford "New Style Torino" brakes: 31-spline, 5x4.5" bolt pattern
QA1 64-66 Ford Mustang Rear Suspension Conversion System - 9in Housing Single Adj. 130lb/in
Single adjustable shocks with 18 settings of rebound/compression control
Includes drain plug, fill plug, vent port, and jack pad for easy service
Weld-in installation with self-fixturing brackets for perfect alignment
QA1 R123-130S Four Link Kit with QA1 9in. Housing Single Adjustable
Complete rear suspension system: 9" housing, 4-link, and coilovers
½" x 3" wheel studs for better fitment with aftermarket wheels
Big Ford "New Style Torino" flanges with 2.5" axle offset
Application-specific fit for 1964–1966 Ford Mustangs
Heavy-duty fabricated 9" housing rated to 800 HP
5x4.5" bolt pattern for wide wheel compatibility
31-spline 1541H alloy axles rated to 650 HP
Adjustable ride height from stock to –3"
Durable semi-gloss powder coat finish
Eliminates wheel hop and axle wrap
1964-1966 Ford Mustang
QA1 Coilover 4 Link
Coilover 4 Link
Suspension Kit
