I'll add my experience to the mix.
I did all of my body work on wooden body bucks, then fitted the body, nose and doors to the car. Once I had all of the gaps to my liking, I removed the body and painted on the body bucks. Even refitting, it took some finesse to have all of the components line up as before.
I test fitted the windshield prior to painting, then installed it after the body was attached.

HTH,
Rob