On the back of the water pump housing there is a small (1/2in) coolant line coming off it. Where does that go?

 

if it's on the top straight up it sounds like the TB line. which goes to the BAC.

there might also be a turbo line on the bottom. I forget where the turbo water lines go.

 

I think the turbo line is on the bottom left corner of the housing (going from memory). But it must be the tb line.

Question: tb mod is done, no bac. Is there a coolant nipple on the back of the engine I can lead this coolant line to? I cant remember.

 

Just route that line into the back of the engine and you'll be fine.