G’Day Eric, Playable Toy Vehicles are really easy as you can adapt and simplify any plan your find to make it strong & safe.
Over the past few years I’ve only used plans for ideas and scaling, but saying that I have heaps of books and digital plans.
All that said I’m my own worst enemy in that I love adding detail with a creative artist flair.
I’m more than happy to share all my know how with anyone who wants to build a playable toy, and I try to do that with photos in the write ups.
I hope that is of some assistance.
Cheers