Our rear bath '66 Trade Wind has only an 11 gallon b-tank. It is a specific shape to just fit into the small area under that part of the floor. I'm sure most all b-tanks are directly under the toilet. If your bath is in the rear yours will be like mine. I had to replace mine 6 years ago and I quickly discovered that the '60s tanks are near impossible. Then the only place back then that carried my tank was inlandrv.com. Very pricey but I was in a cercumstance where I was not able to custom fit an after market tank from one of many resources. I'm now able to plan on installing a gray water tank under the floor behind the axles. An 11 gallon 'poop' tank isn't much but over time my wife and I have discovered when camping we use the trailer tank just at night and bad weather then use campground facilities when we can. It's doable.....and surprising just how much 'crap' that you can cram into 11 gallons
. We can go up to 5 days plus and we have a 'blue boy' to use.
Neil and Lynn Holman
Kirk Creek, Big Sur, Ca. coast.
1966 Trade Wind
1971 Buick Centurion convertible
1969 Oldsmobile Ninety Eight