What is Missing From My Frame...so far

[ChadBice]

I FINALLY got my truck into the garage to start disassembly. My cousin and I took the bed of last night and I noticed a couple of places on the frame where things appear to have been cut off. What is supposed to be here? Also, it I suspect that the rear end that is in it isn't what is should be in it; the tires stick out of the rear fenderwells by about 2" or so. What is the correct measurement from backing plate to backing plate? Thanks!