Bench to Bucket Conversion Advice

Factory nut under the car had a toothed washer about the size of a half dollar. The reinforcement plate was inside the car to prevent the floor pan cracking. There are threads with pics here of floor pans cracked at the perimeter of the factory plate too. Amazing how much shifting body weight along with the weight of the seat stresses a thin piece of sheet metal. Does a clutch pedal cause more shifting that automatic builds? I would check the yes box. I have a 66 drivers bucket seat base frame that was cracked at a hole the factory put in it. No idea why the hole was there but I feel certain clutch pedal use caused the frame to crack there.