Before you choose your spring, you need to understand the difference between Medium duty and Heavy duty. First off the difference has nothing to do with ride quality. Our Heavy Duty spring will not give your Bronco a stiffer ride. This is simply to make sure your Bronco will sit level or at the very least not squat in the back when your Bronco is complete.

Medium-Duty springs are for 66-77 Broncos that have very few add-ons or accessories in the rear. For example, if you have a stock half cab or roadster you would choose medium duty. If you have a resto-mod wagon with a soft top, stock rear bumper, no spare tire, and stock fuel tank, with or without a back seat but not typically using it, then you also would choose medium-duty springs. We do NOT recommend medium duty for trailer towing.

Heavy-Duty springs are for 66-77 Broncos that are geared more towards a well-equipped resto-mod for on and off-road use. If you have or plan on upgrading to a 20+ gallon rear fuel tank, tire carrier + tire, steel plate rear bumper, and/or want to run a hardtop, the heavy-duty leaf spring is also a great choice for your build. These are also the best option if you plan on ever towing anything with the Bronco. If you like going off-road and hitting the trails, the heavy-duty leaf springs are typically the best option for you as well.

For some of you, there will be some combination of parts that accessorize your Bronco in between a soft, medium, heavy, and extra heavy-duty setup. This is why we offer lifted spring perches, 1/2" and 1" lift blocks as well as pinion shims for driveshaft angle corrections to get your ride height and driveability spot on. Our new 1/2" lift block will also offer the option to move the axle back for that perfect amount of tire to fender clearance for the uncut lifted 66-77 Broncos.

Installation Note: The Double spring Wrap aka Military wrap is to be installed towards the front of the vehicle.

You can also add on great upgrades when purchasing these springs like Leaf spring and shackle mounting hardware, Shackle bushings, the Duff HD spring plates, U bolts or HD U- bolts (both that come standard with new HD hardware), HD shackles, pinion shims, lift blocks and new Duff HD weld on spring perches offered in factory and 1" built-in lift.

The 5000A comes standard with our hassle free track bar however we highly recommend upgrading to our bumpsteer eliminator system. It is what we believe is the best steering system for a lifted Early Bronco. This system comes with all of the correct parts to have the correct geometry and eliminate bump steer while giving you a modern vehicle feel. Below you will need to choose a Tie Rod Over or Tie Rod Under Configuration. What is the best choice for you? Choose TRU if you plan only to drive on the street. Choose TRO if you want to go on and off-road. To learn more about TRO vs TRU click here.

TRO - Tie Rod Over will allow for more ground clearance and get your steering system out of harm's way. Axle riser bracket requires Welding

TRU - Tie Rod Under uses the factory mounting locations and does not require a bracket welded onto the axle.

You will need to select the proper knuckle mounting hardware for the steering linkage that comes with this system. If you are not sure which one you need or not sure if your Bronco's knuckles are stock or have been modified then you will need to verify that before choosing.

If you are looking for the strongest or off-road option for your setup then you will want to choose the 3/4" bolt hardware kit. Both of these options may require drilling/reaming and we provide those tools as an add-on once you make your selection.

564X - 3/4" Bolts for TRO or TRU applications - Requires Drilling of knuckles
5661 - Tapered Stud Kit for F-150 / 78-79 Bronco & GM 1-TON Knuckles Tie Rod Under and Over Applications
5660 - Tapered Stud Kit for Stock Early Bronco Knuckles Tie Rod Under and Over Applications

If you choose to drill your knuckles we suggest purchasing our high quality drill bit to make the install easier.

If your knuckles are in rough shape you'll want to consider adding a tapered reamer to clean up the knuckles before installing your new steering hardware. We offer two different options to help with this issue, a 7 degree reamer for your drill or a hand reamer. Hand reamer currently out of stock.