okkkk...this is how my system works...i have 2- 12 1/2 gal side tanks & 1- 20 gal bow tank...total= 45 gal...i have the front tank teed into the drivers side tank line in the back & the 2 side tanks teed together in the back with 1 line going to the stock hi-po fuel pump on the side of the block...i also have a shut-off valve on the front tank in the back incase i dont want to use it...i have n/p with fuel p/u...this set-up is the way the boat came...it is on a 18' in-board ski boat---BBC w/jet...i hope this might help u
P.S. if i was to ever re-do my fuel lines...i would run a fuel block in the back with 3 in-lets & 1 out-let with a shut-off valve on the front tank in the back...incase u dont want to use it