Would've sold about as well as Pet Sounds I think.
I think better than PS, if released in the first 3 months of 67, because the album was wider in scope (than romantic, string-laden ballads) and people were up for it.
Here in the UK, the BBs were voted best group in the world at the end of 66, overtaking the Beatles for the first time, GV was massive, and we were listening to Hendrix, Cream, Traffic, etc - check out the charts for early 67.
After the summer and the San Francisco explosion (earthquake?), tastes began to change.