69 Barracuda - biggest rim size from factory

One option…… The Recall wheel. I'm not sure of it's size. It may have been a 14"-6".

That would give you another 1/2".

The wheel can be seen here at the far right.

http://www.hamtramck-historical.com/images/dealerships/DealershipDataBook/1969/69_Barracuda0017.jpg