Hey Dave,
Love your work. I'm a Dutch modeller building RC and static models in 1:24 scale. We ( my dad and me ) don't use donor models, but our models are completely scratch build. To build them we use brass profiles te build the frame work. We create all the parts we need by hand. I have some pictures includet to show you what we have done until now
this is a chassis of a MAN TGA includig a hand build diff
the diff
this is a picture of the chassis of a Western Star
and some of te parts for the front and rear axles
to give you an immage of the completed models these pictures of the MAN from below
and the Western Star
keep up the good work, hope to see you again
Sjoerd