There was no way I was cutting up the backplate that came with my Browning in order to make spadegrips - I like the idea of having both. Making a new backplate and buffer tube was easily avoided by purchasing another backplate assembly. I bought mine on sale from SARCO for just under $20. It was supposed to be just the housing - I figured it would be no great hardship to move the buffer plate, fiber disks and adjusment srew back and forth and save some more money - but when the thing arrived it was the entire assembly. Cool!
NOTE: On the ANM2, the pin and spring are in the screw and there are grooves on the inside of the buffer tube for the pin to seat in.    There is a hole in the center of the screw on the ANM2 to trap the spring so it does not fly out when the screw is removed, but you can just wrap your hand around the end of the buffer while you extract the screw.

I cut the handle off, and left a small pedistal around the hole where the retaining pin and spring went. This I tapped for a 10-24 allen screw to serve as the new retaining device for the adjustment screw.

This is a 1919 one piece backplate with the handle removed and the buffer tube turned to look like the two piece ANM2 backplate/buffer.
A hole was drilled in the screw to the depth of the spring, then the pin is shortened at both ends. The grooves in the inside buffer threads were first cut shallow with a triangular file, then followed up with the smallest round chainsaw sharpening file I could find. Grind the tips of both files back to the teeth so you get a good, clean termination point at the back of the threads.
NOTE: If you are using angles to mount brackets, skip this step and leave top plate latch stop in place.
Grind off the stop, and make this surface flat and true. It will support the top bracket for the handles.

For the firing trip lever pivot point I welded a piece of square bar stock onto the backplate and braced it against the buffer. I have a MIG welder, but I am no great talent in this area, so it took about 10 minutes of grinding and milling (with a milling burr chucked up in the drill press) for each minute of welding. Also, in an effort to give myself plenty of room for the trip lever to rotate, and keep the trigger pull light, I placed the pivot too close to the trigger slot and it would not fire. Back to the grinder. Good to go, and a nice profile to match the trigger!

NOTE: The closer the pivot point is to the trigger, the more leverage your thumbs have, and the easier it is to fire - light trigger pull, but there is more travel required at the thumb spade. Conversely, the closer the pivot point is to the spade, the less travel the spade has, but a harder trigger pull.

This is the finished "V" spade backplate
with the top 1/2" angle stock welded in place.

At some point you will need to drill & tap a hole in the pivot block for the spring retaining pin. Wait until you have a spring and know exactly where the pin needs to be.

Now on to the Brackets.