Hi Jon,
The Morgan has a PCD of 100 mm, certain models of Toyota Yaris have the same spacing. ( others have 105mm) You need to be wary to get the right one, they seemed to chop and change size of Space Saver Wheel throughout the years, this one was off a 2007 Yaris.
What you need to look for is ,
a 16" Space saver, Toyota Yaris or Aygo
with a 4 J Rim
and 100 mm PCD
most important is that ET 39 is stamped on the rim as that is the offset. ET 39 means 39 mm offset A Morgan Magna wheel has 1 1/2" Offset which as near as can be to 39 mm.
This means the wheel will be central to the forks.
Watch out Toyota also did the same wheels with an ET of 41 and 44. So they are no good.
As I say I researched this in great depth being convinced there must be a production steel wheel that was identical to the Magna. This one fits the bill perfectly.
The larger end of the spacer bobbin needs a small skimming off it to get it to fit inside the Yaris wheel centre which is slightly smaller than a Magna wheel. Once done it is still suitable for use with a standard wheel if need be. The other thing is to machine a 60 deg taper on one end of your Morgan wheel nuts this leaves them suitable to be used for any wheel as Morgan wheel nuts are large and have a large taper each end to allow you to do this. I did both machining jobs in a couple of hours on my lathe, making a simple jig to get the 60 deg angle perfect.
You mention doing the job to your F Type, well although I did not mention it I was so pleased once I saw the wheel was a perfect fit I searched e-bay again and got one from a breakers for £20 + postage, still a cheap conversion and fitted it to my F4 as the F Type is really over the limit with stress on the back end. I fitted a car tyre to the F Type as it is quite a bit more sedate of a drive. Plus the added bonus of 500 x 16" tyres are they are load rated much higher that an Avon SM.
All in all I am well pleased that both of these are now done. I suggest you patiently look for the right one I did note there are quite a few at breakers on e-bay but they want silly money for them, or even try your local breaker when Boris lets us out.
If you need any more info just shout !
Rgds
Ian