Chris Killian provided me with a list of sites containing remaining wreckage from airplane crashes. The following map shows the sites of those crashes in the SGM as well as the trailheads for hikes. All the individual region maps also show the crash sites as well as the hikes. His table giving a brief description of the airplane color and number is available on request. Check his site to see if he has described any particular crash in more detail.
Explanation of map
Map Without Labels
Links for specific crash sites:
Mt. Williamson crash site by Charles Hayden.