Hope someone out there can advise ?

Where do the following go too or come from..........I'm not running a Heater as it's a Track Car.

1) The inlet/outlet on a 4WD Water Pump - it sits at about 8o'clock position and has an ID of about 8-10mm.

2) The very small inlet/oulet on a 4WD Thermostat Housing - it sits at the top exits on the left-hand side at about the 9o'clock position and has an ID of about 4mm.......can I loose this/block it off ?

3) And finally - I have three returns/outlets to my Header Tank:-
One is from the top of my Swirl Pot (no problem), one comes back to the Header Tank via my Turbo Cooler. But where is the larger bore outlet supposed to feed ?

So many questions, so I do appologise