Your best bet might be to hit a boneyard and offer the guy 100.00 for all the wiring you can pull. Some yards will let you do it. OR check around and find a rust bucket that is being pawned off for a few hundred. Thats the cheap way.... You can check E-bay and such but it'll take a little more money and time. Just my .02
Painless Wiring and FRPP both sell the engine harness, but the chassis harness will be difficult to come by without pulling one from a car yourself. I'm not aware of any aftermarket sources for one as of yet.