Thanks everyone for the suggestions. I noticed that AA has an evening flight which does have a 767 with moderately good seats but still, as you say, not as good as DL.
If I book a trip like you suggest, LHR-LAX, LAX-LIM can it be done with one ticket so that in case there's a problem I'm covered at the connection? I don't know much about these things..
I also am considering IB from MAD-LIM as the arrival time is great and I am wondering if I might get the retrofitted new plane.