You can bypass the TB, but if you follow that line through the TB it will go back to the head. The line from the head is there to purge the air out of the top of the motor. You should ideally run it back to the radiator cap side of the radiator, IE a nipple in the radiator tank just below the cap. If you do not have an open nipple on the radiator theres a couple other places, T`ed into a heater hose, T`ed into the upper radiator hose, or drill and tap the waterpump.