One of the most popular modifications for the Mustang II Is to run one of our "tucked" bumpers. The difference between the stock mustang II bumper and the tucked bumper is the depth of the bumper - cars in the 70's needed to be able to absorb a low speed impact. This meant that all bumpers had crash pistons on both the front and rear bumpers. These didn't help much, so they very quickly were replaced with the standard rigid bumpers that we are used to. The tucked bumpers remove the ability to "absorb" the impact and reduce the front and rear dimensions of the car.
There are several steps to installing the tucked bumpers.
Tucked Bumper Installation
To install the front tucked bumper, you'll need to remove the OEM bumper, and the inner crossmember (link to article). You can re-use the crossmember with some modification, but we'll get to that later.
Step 1: Trimming The Header Panel Tabs
The first step is to trim the headlight ears back. There are a few small tabs that are a part of the fiberglass header panel assembly. These serve no purpose and must be cut down to provide ample space for the bumper.
As you can see in the photo, the tab can just be trimmed off. This can be accomplished with a rotary tool (like a dremel) or simply with a saw blade by hand. You can then trim the tab down with a rough grit sandpaper, such as a 60 or 100 grit until smooth. The surface should be flush with the header panel when complete.
Step 2: Adjusting the Impact Absorbers
The front impact absorbers need to either be moved back on the frame, or pushed in to allow for the OEM crossmember to be retained. For the purposes of this installation, we are going to move the stock impact absorbers back on the frame.
To accomplish this, we are going to remove the 2 bolts that attach the absorbers to the frame of the car. You can then drill 2 new holes behind the existing holes on the bracket (see image). These holes should be drilled approximately 3 inches to the rear of the existing holes.
Step 3: Mounting the Front Bumper
The front bumper itself should be independent of the crossmember (it will not bolt on directly to the crossmember. In fact, it only attaches to the header panel (where the grill is) and the quarter panels. Simply drill two small holes on each bumper flange (where the bumper and quarter panel meet), and mark those spots on your front fender. Then drill the fender holes and install hardware.
Step 4: Final Adjustments
If there is a gab between the top header panel and the front bumper, this can be closed by adding additional nuts/bolts or screws. This will suck the top end up and remove any unwanted gap (note some gap is normal, and the original bumpers had a small gap.
Step 5: Installing Crosmember
Now that the fiberglass bumper is installed, you'll want to reinstall the front crossmember for safety. The impact absorbers will be further back on the frame rails, so be sure to account for that.