I'm Sorry, I Dont Have A Pic. The Assembly Manual Shows The Part As A " P Washer". I Assume It Is A Thick Washer/spacer (1/2" ??). I Know That Firebirds And Camaros Do Not Have Them, As I Have Never Seen One On The Many Cars I Have Disassembled/ Assembled.
I've been looking into this as I am planning to replace my body mounts on the '72. Check the AIM page again... If it's like the '72, each mount gets a "P Washer" and it goes below the sub-frame and should come with the bushings. On the rad support mount there is a "Spl-Washer" (#2) That is used because the bolt goes in from the top. On the middle mount there is a spacer "spacer-spl" (#16) that goes above the upper sub-frame bushing and below the body...
Stacked it goes like this;
Core Support ...... Center Mount ...... Rear Mount
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
bolt ................ body (cage nut) ... body - cage nut
washer ...........
spacer ................ cushion asm
cushion .......... cushion asm ........ sub-frame
core support ... sub-frame ........... cushion
cushion .......... cushion ............... washer
push nut ........ washer ................ bolt
frame ............ bolt
washer
lock washer
nut