SSassasins

So here's my general question to you guys. I'm a at home mechanic, pretty good building skills but need advice on this one. I've accuired a Workman 3 wheeler for free. It's all in all in good shape but am wanting to make it my own. Is there a way to run a fixed gear hub on the center axle? And is it possible to slap on a set of surly rolling darryls....I'm new to the 3 wheel world and just can't find any info out there! Any help would be appreciated!