The wire harness is a summitracing.com thing.
The suspension pieces were bought locally through a circle track speed shop called lawrence engineering out of trenton, NJ.
http://www.lawrence-eng.com/
They are a good bunch of guys, and if they get to know you they start to cut people deals. They are great at giving advice and helping with technical solutions. They design and build dirt track cars, so that is their main business, but they also do some (read very little) motorcycle stuff, and helped modify the locost chassis once (mine). I don't believe that they do internet sales or mail order, but they have a very nice sized stock in their store, and a full service shop in their garage where they build the chassis.
The suspension pieces cost me a hair under $250. I could get the stuff cheaper on the internet, but they have given me lots of freebies, checked welds, bend pipes for free, and cut alot of my chassis tubes without cost etc... so I figure I pay more now for free stuff later. Plus they will take a return on a part that I damaged, and replaced it free, no questions asked.
Also if you are in NJ at the end of Novemeber they have a great flea market, and you can get almost anything you would need, it's mostly dirt track stuff, but last year I scored a nice set of wheels, a bunch of used power tools, and the guy I went with bough an enclosed trailer complete with it's own (slightly damaged) race car.