Re: Head suggestions for 20" Kick
Try a black dot as your batter and a regular coated ambassador on the front with no hole. Use felt strips on both sides, or just use one on the batter side if you want a bit more ring. That'll do it. In a live situation if you're not miked up, nobody will hear the extra ring but you anyway.
Old skool sounds require old skool methods. EMADs and Powerstrokes didn't exist when they made the sounds I think you're looking for ;)
Good luck on your quest!