You can replace the pans without removing the body unless you just want to for the heck of it.  Its not hard to do just a pain in the butt. Take all the wiring loose at the engine, heater hoses from the engine to the body, Master cly wiring and brake fluid hoses, fuel hose at the gas tank (You can take the tank out to lighten the load)   steering shaft at the box, all the bolts around the pan underneath the car. 17mm bolts(one per side) under the rear fenders on the shock mounts,  13mm bolts across the pan inside the car in the back by the shift coupler .  Take the seats out so you won't have to lift it so high .  I,m sure I have missed something but if any wire that goes from the chassis to the body , take it off at the pan. All wires stay with the body.
      Then find 4 strong men or 6 weak'ns , shake the snot out of the body to break it loose. If it doesn't come loose, go find the bolt you forgot take out.
      I guess you do know that the '68 has a swing axle and your '73 has IRS if it makes any difference to you.
     See, its not hard to do .Its just a pain in the arse  . Have fun !!