Morgan went with the S&S engine because they could get it cheaper
Not so, they approached Harley who wanted a minimum order of around 5,000 units. As Morgan couldn't do this it was HD who suggested they go to S&S.
Moto Guzzi were also approached I understand but with minimal introduction such that they were not interested.
I believe that was for a replica that was intended to be made in 100 units for the Morgan 100th anniversary by Triking. Tony Divey, the owner of Triking, was in failing health and only a prototype was partially constructed. Moto Guzzi wanted too much for the required components (not much less than the cost of a complete bike) and that, in combination with Tony's health situation, put an end to the project.
If the project had gone ahead, as I understand it, it would have had little to do with the Morgan company.
The eventual 3 wheeler was inspired by the Liberty Ace which used a HD engine but the eventual desifn was so different that one can only say "inspired by".
It is a rather curious sequence of events that the M3W was inspired by the Liberty Ace, which in turn was inspired by the Triking (Pete Larsen had tried to buy one), and, of course, the Triking was inspired by the original Morgan 3 Wheeler. Full circle
