How do you remove the modulator on a 1967 Chevy truck?

Assuming this is a PowerGlide or Turbo-350 automatic transmission vacuum modulator, to minimize fluid loss jack up the rear of the truck and support with suitable jack stands, place a drip pan under the modulator, pull off the vacuum line from the modulator, remove the small bolt and clamp holding the modulator in place, gently twist and pull the modulator out taking care not to lose the small actuator pin inside. Keep the dirt from entering the opening. Install the new modulator with a new o-ring.