When I bought my car, its high-mount globe had melted, but the holder/thread was fine. I went to the trouble of pulling the carpet out as you are saying, and the carpet is an absolute BASTARD to try & put back in without any crinkles! Also, the woodchip/insulation stuff under the carpet had turned into flaky/caked dust, so it was time for Mr Vaccum again! When I pulled the box out after fiddling with the clips, I found that I couldn't get the box apart.
Instead of "removing" the bulb the easy way by half-screwing it out, smashing it by hitting its base with the back of my fist, & then vaccuming the bits out thru the screw-hole, I had pulled up the carpet & half-pulverised the decaying insulation before I found that it was a waste of time. I ended up smashing the bulb anyway!
It's amazing how even E-series Falcons can be maintained caveman style!
Oh, the carpet fitted fine back over the decimated insulation after several attempts to get rid of the creases/crinkles, but I burnt my @#%*ing knuckles on the back window SO many times it wasn't funny (hint: don't park the front half of your car in the shade if you're gonna work on the back half).
Gotta go to work now,
'91 EB Fairmont Ghia V8.
Pacemaker PH4000 extractors
Meaty semi-twin system
AUII XR8 t/b & maf, ELGT snorkel
BA semi-manual shifter conversion
Electronic shift kit
4.11 Hydratrak LSD
Explorer intake manifold
Contra 16x9 rims, rubber: 225(f)/245(r)
Chiptorque HP2 chip
ET: 14.78 @ 91.48mph, 137rwkw!