304AH * 16 = 4,864 AH (@ 3.2v nominal)
4,864AH / 40A = 121.6H (5 days)
The fastest way to charge them would be to connect them in their final configuration (4s4p) and charge them at your desired voltage (i.e. 3.45v = 13.8v)
304AH * 4 = 1,216 AH (@ 12.8v nominal)
1,216AH / 60A = 20.3H or about 5...