I was the one who originated the thread above. I followed MonteZooma’s advice and all was well. See my acknowledgement at http://www.talkmorgan.com/ubbthreads.php/ubb/showflat/Number/117106
The only thing I would add was that at the start I had to pull the mirrors out with more oomph that I originally thought would be necessary. At the end of the original mirror stem was a round clip. I took this off but could not re-fit on the replacement mirror stem, which had a slightly larger diameter. A couple of windings of duct tape ensured that the new stem slipped into the base and was held tight with no rattling. 100 or so miles since I did this I am very pleased with the result.