sounds like you found a good donor piece for your burb.
I looked for the mag i seen the flush cap mod done in and couldnt find it. sorry
I just happened to stop by a local cruise in i dont normally make it to and there was a panel there ,i saw as i was leaving i jumped out to get a few pics but didnt have time to track down the owner im going to have to make it back out there and try and catch up with him cause this looked pretty good and id like to get all his info and tricks LOL
Smooth flush gas door on 47-54 panel another angle and another angle