Here is the replacement front...
Here is the replacement front stub acquired from Freeman Auto, removed from a salvaged front clip. Note that the entire front frame is intact from the transmission crossmember forward between each of the rocker panels. By keeping the transmission crossmember as part of the unit, we will have no problems with motor mount and transmission crossmember locations. All critical measurements are maintained by replacing the front stub in this manner.
In the January issue of Mopar Muscle, our installment on the Holley Project Roadrunner covered the topic of media blasting. When it was all said and done, it was apparent that the investment of $4,300 in this B-Body was showing true signs of its bargain nature.
However, just because rust had set into the front frame rails and other significant structural components doesn't mean the Roadrunner wasn't a worthy candidate for resurrection. In fact, with the skills available to the project-specifically those of Muscle Car Restorations of Eau Claire, Wisconsin-we knew that while the work seemed ominous, the craftsmanship available would step up to the task ahead.
After sandblasting the body at DeWayne Krumenauer and Randy Goettl's Progressive Stripping in Chippewa Falls, Wisconsin, we were down to the bare elements of the Roadrunner. What would lay ahead was in plain view-replacement of the front stub/front structural clip.
John Balow noted, "Because the frame rails were very rusty and the torsion bar mounts were questionable, we felt the best method to ensure structural rigidity would be to remove the front stub. Other reasons to make this major repair would include if the car you are repairing had been in an accident and the frame rails were bent."
In this photo, it is apparent...
In this photo, it is apparent that John's crew at Muscle Car Restorations have ground down the spot welds to guarantee a flat surface for the frame box to mount to the unitbody. Note the corrosion-free torsion bar mounts.
But where do you find a complete, intact front stub that extends from the transmission crossmember forward? Balow turned to Neil Freeman for the replacement sheetmetal. Balow ordered the front third of a '69 B-Body and the craftsmen at Muscle Car Restorations carefully removed the front stub from the donor car body.
As you know, alignment is critical with such a swap, and the front stub, when complete with the transmission crossmember, offers an excellent way to guarantee exact placement of the motor mounts, transmission crossmember, and other critical measurements.
The question most would ask is, "Does this constitute a re-body?" In a manner of speaking, it does. However, if smaller areas were replaced, the splicing and welding would be far more apparent than the exposure of the front stub with replacement or original sheetmetal. "We don't want it apparent that the car has been reframed," said Balow. "What we do want is to reassemble the car with factory spot welds. It is not 100 percent undetectable, but it can be very close to perfect with a lot of tedious work."
Of particular note with the Holley car were the torsion bar mounts. Rather than risk a torsion bar failure, as well as other structural issues, the replacement front stub grafting to the original unitbody was the only option John would consider.
Follow along here as we demonstrate the work involved to make the repair.

Jason Balow of Muscle Car...

Jason Balow of Muscle Car Restorations sandblasts the front stub/clip acquired from Freeman Auto. Extra care is taken to remove all residue and to paint both inside and outside the frame rails.

After the front stub is sandblasted,...

After the front stub is sandblasted, it is ready for installation however, extra effort is made to coat the inside of each crossmember and the inside of the frame rails as best as can be accomplished with POR-15. This will aid in keeping corrosion at bay.

Here is the Project Road Runner...

Here is the Project Road Runner clearly missing the front stub. A Muscle Car Restorations craftsman makes final repairs to the inner passenger side rocker panel.

This patch is a repair of...

This patch is a repair of the inner rocker that had rust. Note the attachment point for the transmission crossmember (arrow).

A great deal of care guarantees...

A great deal of care guarantees that all mating points for the front stub will align and fit securely. Part of the installation process to the car body is to eliminate any burrs and create a flat surface to mount the front stub.

Awaiting several helpers,...

Awaiting several helpers, the front stub is readied for installation to the unitbody

Once alignment is set to a...

Once alignment is set to a desired position, a host of C-clamps and Vice Grips(tm) are used to secure the front stub to the unitbody. Both are sitting on the alignment table. All critical measurements are double checked to guarantee proper fitment.

The spot-weld process has...

The spot-weld process has begun where the front stub has been attached to the unitbody-specifically between the inner fender and firewall.

Where the front stub meets...

Where the front stub meets the rocker panels, John McDougall-a certified welder and expert metal fabricator at Muscle Car Restorations-is plug-welding the floor to the inner rocker panel, the transmission crossmember, and the front frame rail. Once this is accomplished all the welds are cleaned up.