On most Bay windows it's all the same rust areas, lower windsheild area, Front driver and pass floor area, inner splash area (behind front wheels) battery tray, sliding door track and always chech out riggers, jack points and in very rust buses the frame in front of the torsion housing.
If it's a 1970 the fuse boxes are bad, they tend to weaken over time and crumble.
What year and model are you looking at?
