The back of your door is somewhat similar to my 1975 Williams Little Chief door, but not exactly. I'm in the middle of cleaning/refurbishiing mine so this is a bit sketchy, but here are some pictures that may help.

The first is the coin mech itself. Each mech has a pair of pins as shown here at the bottom:
0901151037.jpg

These will fit into the plate at the front side of your door as I try to indicate:
0901151039.jpg

Each mech also has a retaining plate on the side opposite the pins:
0901151038.jpg

This plate clips into the spring retainer clip just above the coin switch on your door:
0901151041.jpg

Note that my game did not have any coin mechs when I got it; I picked them up on Ebay. When they arrived the pins I show were on the other side, which was a bit confusing for a while. Also, they did not have the plates; I ordered from one of the pin suppliers (I'd have to dig through my notes/receipts to figure out which).

So basically the pins locate the mech on the door, and the plate/spring locks it into place. Hopefully this helps some; I've been a lurker on here for a long time and this is my first attempt to give back for all I've learned!

I checked back, and got my retainer plates from Marco Specialties. Here's a link to the part; I'm sure other suppliers probably carry them as well: http://www.marcospecialties.com/pinball-parts/1A-4253

As to the other piece, I don't have a clue. Not sure what it's called, which seems to be the best way to find things.

Good Luck!