OK, I did some research and it seems I have to admit I was wrong (how about that, PC?). My apologies.
Regarding the stereo versions of 'I Get Around' and 'Good Vibrations', this is apparently the deal... I hope this will clear everything up.
'I Get Around'
The real live version of 'I Get Around' was, like I said, not good enough to be released on the 'Concert' album. I can send you the real live version from August 1, 1964 in Sacramento if you want to hear it.
The Beach Boys then, like I also said, re-recorded it in the studio.
But that's where I went wrong. After recording six takes of the "new" backing track I was talking about (all six takes been bootlegged on 'Unsurpassed Masters Vol. 6'), the band decided to just record new vocals over the backing track of the original studio version, and add fake live noises.
Apparently some bright spark decided to use the original multi track master tapes for this without making any backups or anything. And in the process, the original vocals were erased from the master tape! So the version that ended up on 'Concert' is the original backing track, remixed from the original multi track master tape (I assume the guitar solo was on a seperate track and left off this version because it sounded too good to be recorded live), with new vocals, and with live sounds added. If you're not buying that, I have a recording of the vocal overdub session that I can also send you.
So the master tape of the original studio version became the master tape of the 'Concert' version. That's why it has been assumed that the released instrumental backing track was not the original backing track but one of the new recordings made for 'Concert'. To be exact: it was Brett Elliott, author of 'Surf's Up: The Beach Boys On Record 1962-1981', who made that claim and since he was considered an authority on all things Beach Boys people took it as a fact.
So the reason why there can never be a stereo mix of 'I Get Around' with vocals: the original vocals have been erased from the master tape and all mixdowns that were ever made were in mono. However, a stereo mix of the 'Concert' version with the "live" sounds stripped off should be possible, I guess.
The multi track tape of the backing track is still in the archives.
However, the tape that the backing track was transferred to and where the vocals were recorded on has been missing ever since a massive clean-out of the Columbia Studios in 1967.
That's why it's not possible to make a stereo mix of 'Good Vibrations' with vocals. There however is a stereo backing track of 'GV', it was released on a 'GV' 40th anniversary cd-single in 2006. I could send you that as well.
So the original version of 'IGA' being released in stereo is pretty much impossible, 'GV' being released in stereo is highly unlikely.
But then again, you never know. The master tapes of the 'Shut Down Vol. 2' album had been missing since 1964 and turned up in a private collection earlier this year. The newly found master tapes have been used to make new stereo mixes of the songs 'Who Do Fools Fall In Love?' and 'Don't Worry Baby'. Both have been released on the compilation 'Summer Love Songs', which came out about a month ago.