I use Penrite HPR5 or HPR10 for my RB25.
Gearbox is either castrol, nulon or penrite these days. I just use average oil because I abuse boxes.
In my R32 diff I use either castrol or nulon 85/130, in my R31 I just use 90w.
Coolant is premix 90-something and just top up with water until I empty it all.
I do go through fluids more than normal because of what I do . Price varies alot, just look out for sales or 20% off days.