Wow! Where to begin?
Personally, I do it in the following order:
1. Drive train (engine,tranny, drive shaft, pumpkin, brakes and brake lines)
2. Cab minus doors, minus seat. Install gas tank if behind seat.
3. Master brake cylinder, heater core/blower, brake/clutch pedals and linkage.
4. Radiator support, radiator, hoses.
5. Inner fenders.
6. Wiring - engine, cab, lights(leave for future connection).
7. Instrument cluster, heater, radio.
8. Outer fenders, grill, head lights, front bumper.
9. Install wood in the box off of the truck.
10. Install box.
11. Tail lights.
12. Seat and doors.
Maybe that's too generic. Get a manual, and some parts catalogs. Also, check out Tony's site,
www.4-5-6chevytrucks.com he has so many photos. Another good site to visit is:
http://lugnutz65chevystepside.weebly.com/Good luck and keep us updated. Wish I lived closer.