Camaro Work

I am losing water from the cooling system on the Camaro, but I'm able to quantify it to about 1/2 gallon for every three tanks of gas. I'm pretty sure it is a head gasket leak.This could also be cause of "knocking" noise I have on some startups. But I've decided to drive the wheels off the Camaro, so fixing some things:

1. Repaired air conditioning. NEX autoport did the work. They charged about $350 less at $650 than Goodyear was estimating.
2. Oil change while repairing AC.
3. Oil pressure sensor leaked right after oil change. It is right above the oil filter. Coincidence? Eh. Hardest part of the repair was not having right wrench to screw it on with.
   
4. Turn signal relay. Right turns would sometimes just come on solid and not blink. Seems to be working.
5. High beam dimmer switch. I bought a replacement, but it is not broken, just sometimes hard to get to switch. The switch is in a very difficult to get at location, so I think I'll let it be for now.
6. Started some work on rust around the battery. I need to remove the plastic base, but I do not have the tools with me to do it. Put some Rustoleum Rust Converter on the rusted areas. We'll see how that goes.