NOTE 1:  Distance between the front threaded studs for bumper mount scales as 22-1/4 inches on my drawing, measured as 22-1/2 on one frame (probably straight) and 22-3/4 on another frame (probably bent). The exact original design dimension was not known when this was published.

NOTE 2:  The exact original design dimension between sway bar mounting holes was not known when this was published. Measurements vary on a single frame and also vary from one frame to another. I would speculate that these holes (for the later issue frame) were punched in the flat stock before forming. Exact location left to right is not important, as long as the brackets fit. A slight variation of width between mounting brackets does not affect function of the sway bar.

NOTE 3:  All of the mounting interface parts were originally fixtured for welding, so all mating surfaces, studs and holes should be in correct locations. The cross tubes were apparently not conistent in form, so position of the ends of the tube could vary in height relative to the end plates. It is common for ends of the tube to be lower than center of the end plates. End plates sit at 45 degrees. Pedestals are rotated 30 degrees.

NOTE 4:  Top edge of the guide for starting handle has been measured to be 1/8" higher than top of the body mount pedestals. Even with frame to body packing in place this makes the crank guide interfere with the horizontal air pan on the body. It is presumed this is intentional to bend and preload the panel slightly upward to inhibit vibration of the panel.

Materials: The round cross tube is 1-1/2 inch O.D. 14 gauge steel tubing (0.075" wall thickness). Sheet metal parts are 14 gauge (0.075" thick). Left and right end plates are 11 gauge (0.120" thick). The front studs are 13/16" diameter x 4-3/8" long (before machining the threaded ends).

Addendum June 9, 2023:
This additional drawing, provided by Bob Shafto, shows locations of holes for horn mounting brackets. The two holes on horizontal alignment 2-inches from bottom were original issue for MGA 1500 cars. When the top notch was added for sway bar mount, two more holes were added each side for horn mounting in more forward position. Those are the holes at angle 1-inch from bottom near the front of the frame. The 1500 type frame would have only the first two holes each side. The 1600 type frame would have all four holes each side. Adding the two forward holes can be part of the conversion process to modify the 1500 frame to 1600 specification (see next page).