Quoted from NorCalRealtor:
What spare parts? Are you speaking from experience? When I received a replacement lower cab from Stern it was completely bare. I had to disassemble the entire pin and swap over every single piece and nut.
Perhaps things have changed, but I saw a replacement Aerosmith cab, and it had lockdown bar receiver, plunger, start button, most of the harness, leg bolts, and more.
I saw a video of someone with an AS cab that had the same, but they may have changed policy.