Might be worth having a chat with Dan White
Suspension Supplies Ltd Suspension Supplies Ltd was formed by Dan and Peter Ballard when Suplex decided to concentrate on replacement springs only. Dan and Peter at SSL are now producing the SSL RS and SSL 5L front and rear suspensions for Morgan. I know they were thinking of doing something for the 4 seater but I have no idea if that project has moved along or not.
I see from their web site that they are looking at single leaf composite springs for classic Morgans. That could be a very interesting development as it would not require any modifications to fit and offer the advantages of no stiction (such as you get between the leaves of multi-leaf springs), light weight and durability.