If it were me.....I am thinking that you already have the frame/running gear all put back together and engine, tranny, rear end back in/on the frame.
From there, I would mount the cab. Once the cab was on, I would start the wire job.
Run the truck and make sure your engine and wiring are all up to the task.
Finish most of the details on the cab including all the mechanicals connected to stuff under the hood. Easier to work on the firewall side without the fenders in place.
Then the front end, starting with the radiator frame. Build your front end up. Finish the wire job.
Running boards next.
When done with that, box without the bed put together off truck.
Lift into place onto truck.
Then install the bed. I must confess, I have not done a bed yet, so I am guessing as to when I would install. I work alone so lift weight is always a factor for me.
I am probably missing a whole pile of important stuff. If you are looking for "what to first, then..." That's what I'd do....
