Leaking rear end 1967 Barracuda

If it's the pinion seal remove the driveshaft remove the pinion yoke nut and use a puller to pull the yoke off the pinion use a seal puller to pull the old seal out. Inspect the seal surface on the yoke and clean it up with some crocus cloth if necessary replace the yoke install a new seal and reinstall the yoke and nut and torque the nut to 240 ft lbs. reinstall the driveshaft and check the fluid in the rear axle. Note the early 7 1/4 axle has a shim for pinion bearing preload so changing the seal will not effect the preload. That being said worn out bearings or damage from being run low on oil can cause wear on parts. If it was mine I would tear it down and inspect it for further damage and rebuild it back up. I am also not advocating rebuilding it with all new parts good bearings and gears do not need to be replaced. Clean inspect and replace what's bad.