Just thought i would throw this at the would be builders for a low-cost, high gas mileage, easier than most to build trike.
It's like a lotus style chassis build and you can decide what kind of body you want. I also like that it is Front wheel drive and a side by side 2 passenger cabin.
UPDATE: The name on this picture stuck in my mind as i have looked at this trike for many years. The chassis is really a XR-3 design, not the trimuter. The trimuter is a single front wheel trike based on the volkswagon drivetrain.The XR-3 is a completely different animal. It has a gas or diesel FWd drivetrain along with a optional electric powered rear wheel. You can read about it on Riley's website. rqriley.com/product/xr3-hybrid-plans/