Yes the entire back seat must be removed in order the remove the inside quarter trim panels. So far the job is a little more difficult than making a cup of instant coffee!
Now theoretically you can get in there and put the speed nuts on the ornaments. I don't recall what is used on the 66. The 68 uses speed nuts.
Messing with the quarter windows is a whole different experience. It's not rocket science but helps if you're handy! Once you mess with them aligning to the top and the door window takes patience and several adjustments that aren't obvious at first.
My '64 1/2 vert. Ordered May '64. D code 4 speed, handling package, caspian blue, accent group, Ford blue manual top.
'68 vert. driver. Owned since Apr '78. C code AT, AC, PS, P disc B, PT lime gold, standard black interior and top. NOS RF fender and left quarter.New top and folding glass.