First, buy the '57 Mini Twin-Amp and give it a listen.  Play through the speakers and through some headphones.

Then run a guitar cord from the headphone jack to your amp input and stand back!

Start with the Mini-Twin at Volume "0" and slowly turn it up.  This will demonstrate the kind of effect to expect from this project.

To repurpose the Mini-Twin to a dedicated stomp box, we need to:

• Replace the speakers with a dummy load.
  
  
• Reduce the overdrive volume to a level more compatible with the straight guitar volume.
  
  
• Add a true, hard-wired bypass footswitch and LED.

We will utilize the existing input jack, headphone jack (for output), power jack, and battery holder.

Work begins by removing four screws from the cabinet's rear panel.

Then pry off the back with a small blade screwdriver.

Next, remove two screws holding the headphone-jack assembly to the cabinet's side . . .

And two screws holding the battery compartment to the rear panel.

To complete the disassembly, remove the amp chassis and the speakers from the cabinet.

The amp chassis mounts with four screws passing through the handle brackets, the wooden top, and the metal chassis plate.  The screws thread onto nuts with lock washers inside the chassis.

The speakers mount to the front baffle with eight screws.  You can unsolder and remove the yellow and green wires connecting the speakers to the Jack PC board.  These wires won't be needed.

Next, drill two holes in the rear panel, which will be the top of the stomp box.

Then mount the 3PDT footswitch and the LED & holder.  The placement shown here poses no clearance problems when closing up the box.

This photo shows the switch and LED from the inside.

I had to countersink the LED holder's mounting nut becacause the threaded bushing wasn't long enough to pass through the whole panel.

The threads on the switch bushing were plenty long.