Hi Andy !
The next step probably would be to find out about all the other
a/c in the given list where no crashsites are given. You could try to find each bomb groups homepage as a lot of the heavy bomber groups have one. Then contact the website's staff to learn more.
It's well known that it is quite difficult to match individual Luftwaffe claims
with the actual allied losses since there are "overclaims" (on both sides).
Some more hints:
-try to google for the serials
-
http://www.armyairforces.com/forum/
-
http://home.att.net/~jbaugher/usafserials.html
bye,
FrankieS