Apps like audiohack, shntool, wavmerge, etc., are all good for merging two audio files. The question then becomes: does one's audio editor handle WAV files > 2 GB? If so, great. If not, merging the files doesn't help, in fact it hurts.
I forget if Audacity handles stereo WAV files > 2GB. If so, again...no problem. But if not, there's an easy workaround - simply import both original files into Audacity, align the start of the 2nd with the end of the 1st, then edit, track, and resample/dither as required while exporting to individual tracks.