Joe Tocktrop's American Beauty is a 1/4 scale model based on the Economy, but it is not a true scale model. 7/8" (or 1" ?) bore. Castings mainly aluminium. It has the reputation of being a good runner. Many hundreds of kits have been sold, which should speak for itself.
You are probably aware that Joe Tochtrop does not have a web site (or email)
I haven't heard of the Bishop Repair model. Would you please let us have details on this previously unknown (to me) supplier.
A third supplier, in the UK, of a 1/2 scale Economy is The Engineers Emporium.
http://www.theengineersemporium.co.uk/catalogue-pages/petrolengkits.html
Dave
The Emerald Isle