If the red tranny fluid is coming form the bellhousing, then either your front seal is gone, the converter has a leak, or the pump housing O-ring has gone south.
All the factory converters have a drain plug, it could be loose. Remove the round rubber plug from the botton of the bellhousing and rotate the engine IN IT'S NORMAL DIRECTION OF ROTATION, until you see it. If the tranny has an aftermarket or rebuilt TC, it MAY NOT have a drain plug. If the TC drain is not lose, and the housing is full of fluid, you will haved to pull the transmisssion for further inspection.
The front (stator shaft) seal is commonly available, it's about $5.00. Check with your local APD or Transtar dealer, or Ford. The pump flange gasket and O-Ring are available from the same locations, and should cost about $6.00. The front of the trans will have to come apart to replace the latter.
If I have misuderstood your question, and you actually need a tailshaft housing seal (more common), same places, equivalant prices. Remove driveshaft, pry out seal, CHECK BUSHING, replace seal, wipe grease on the lips of seal, replace driveshaft. If the bushing is worn, no amount of new seals will stop it permanently. Remove housing and take to machine shop to have new bushing pressed in.