I've collected 139 hotwheels sized cars, which I thought were interesting to designing styles for three wheelers. Of those, 13 are actual three wheelers, the other one has got kind of a 'spare' wheel. I attached a photo of them. 5 of them I cut out of other hotwheels, and some are just in that match-box size category, not actual hotwheel or matchbox cars.
Trike motorcycles are much easier to find, I don't collect those for study. They don't have an interesting body to me.
Three of them are 1F2R and the others are 2F1R. 2F1R is very hard to find in any toy or plastic model.
I particularly like the streamliner in the photo below, front left. very-very hard to find one of those. I think it was for actual racing performance, looking at the razor wheels it has. All the toys below have the front facing the same direction, in case you wondered.