Lots of various changes in the cabs over the years. Best to get a cab of the same year as your truck. Yes they all will interchange though.
72-74 have an obvious rounded shape to the floor beside the seat when you open the door and look down. They also mounted the jack on that rounded hump on the passenger side.
72 cabs have a pipe welded to the cowl for the heater blower pipe, and use a spring clamp to hold a flex hose, and the 74 and newer cabs have a hole where a plastic moulded pipe fits in.
All rear window openings are the same. It is the glass and rubber that are different.
Several floor hump versions over the years. Small hump for 2wd automatics, medium removable hump for some 2wd manuals, large removable hump for 4wd and some 2wd manuals,
All firehall heater openings from 72-80 are the same size.