The recip-saw should do it. I cut the bolts on mine off with a dremel and a cut off wheel. It is a tight space. Note that the plastic insert molding that hides the rivet lines in a 68 bathroom is not available anywhere. I spent a year trying to find some with no luck. Take care with it if you remove parts from the bathroom as you will need to reuse it.
Once the toilet is off, the closet flange unscrews from a short pipe that connects it to the threaded flange on top of the black tank.
If I remember I used a big punch and hammer to get it started. The floor in my 68 was rotten so the screws holding the flange down were gone, if your floor is good then you will need to remove those first.
Bruce & Rachel
68 Trade Wind
2001 Toyota Tundra