Once the Front and Rear Axle Centerlines have been marked, the body was removed from the frame and the frame cross-measured. The frame should be within an 1/8″ of square. If it’s not, you’ll need to straighten it. Also have the frame sandblasted. Paint, body filler and rust can hide cracks and weak points in the frame.

After numerous radiator mockups and much deliberation over various other factors, Mark has chosen to use our full length boxing plates, Tubular X-member and a Direct Sheetmetal recessed firewall ( See Step 8: Body Modifications).

What Mark encountered is one of the true “pitfalls” in building a street rod that nobody likes the thought of doing, changing the firewall. Doing this to allows the motor to be placed farther back and higher for clearance of fans and a radiator effective for cooling the motor. Also changing to our tubular X-member allows Mark to get the automatic transmission back farther as well, and adds strength and stiffness to the frame.

Our X-members are designed to allow you to place the transmission where the motor dictates it. With our X-member you can run any of the popular transmissions. We do custom build these for the Gear Vendors overdrive units.

While doing these changes, Mark stresses the value of tack welding things until you are sure that they’re right!

A temporary tube was tack welded into the frame to keep it from springing while removing the original crossmember. When boxing the full length of the frame, remember to weld in nuts for all of the mounting holes in the frame.

Straighten the top and bottom lips so that they are square with the sides. Mark used a 15″ adjustable wrench to straighten his.

Next, the boxing plates were installed and the welds were finished and smoothed.

The tubular X-member sides were leveled and the crossmembers were welded into place. The X-member was placed into position on the frame. The blue tape indicates where the excess of the X-member will be cut-off for a tight fit into the frame.

With the X-member in place, the position of the transmission mount will be determined with the placement of the motor mounts.

Once the motor mounts were tacked welded into place ( Step 4: Motor Placement, Exhaust Manifolds, LT-1 parts & Gas Tank), an aluminum block served as a shim between the X-member transmission mount and the rubber mount. After double checking squareness and angle of the motor, the X-member transmission mount was tack welded to the X-member.