Im going to be replacing my radiator in my RS soon and I was wondering what I should fill it with. Also should I replace any of the hoses just because I'm there? Any other parts I should as well?

It's got 129k on it.

Also what should the timing be?

 

I filled mine with the green premixed antifreeze. I replaced my hoses as well since they're not too expensive and I didn't know how old mine were. You might want to check your water pump and heater core while you've got the coolant drained. I ended up replacing these as well but in two separate jobs. It would have been much easier to just do everything at the same time.

 

I think I will definitely be doing the hoses for sure

 

timing should be 0 but when I had the old 305 in the car I had it about 2-4 degrees

 

Wouldn't hurt to do it all.
I usually do all the hoses, so one dosen't age and wear out, then another.
As far as coolant it dosen't really matter. You can run less coolant and more water in a hotter climate and it will cool better.

 

At the least, do the lower hose. If you have an electric fan, remember that the bottom two bolts can stay attatched! Removing them only makes a headaches sticking you're hands where you don't want them later on. I use straight antifreeze/tap water mix 50-70% being antifreeze (in NY where temp dips under freezing). 50/50 premix is just as good but just more expensive when you add it up. Also, don't forget new hose clamps! On rare occasions the old ones break, but just having the new ones on makes it look a touch better assembled.