Question on Vehicle Design

I was planning on designing some vehicles for a Cepheus game and was looking for some advice on vehicle design books.

There seem to be two Cepheus vehicle design books available (If there others, I'd love to know about them).

One is the Cepheus Engine Vehicle Design System from Samardan Press. The other is the Vehicle Design Guide from Moon Toad Publishing.

Has anyone used these? What are the differences between them? Anyone have a preference?

Also, do any spreadsheets exist for Cepheus Vehicle design?