Well heres what I did in my 02. The stock piece was just some plastic that somehow was broken by the previous owner or something
Went to home depot and got some 90 degree steel stock and some flat stock (its usually near the nuts and bolts)
I measured the width of the opening inside the dash. Should note that you need to measure to the inside lip on each side so that it will slide into the little reliefs on the console/dash. Also a good idea to take those measurements at about where the radio will be sitting to ensure a good fit.
The support bar just goes straight back, if theres nothing for it to rest on u can add something in there but there was a metal brace inside the dash that mine rested on.
I took the double din trim piece that my new radio came with, centered it on the bracket, marked where the bolt holes were and drilled/tapped them.
I also drilled holes on each arm on the 90 degree stock where it will get bolted to the dash.
The blue arrows are where the radio will attach, the red are where it gets bolted to the dash
Heres a pic of it in the dash (ignore the mess of wires)
Circled in red are the two bolts holding it to the dash, the green is just the support bar going back.
radio installed. Green just shows where the trim kit/radio attach to the new support.
trim piece installed hides everything