Technical Unknown Fluid Types - Advice (Pic)

Making progress on a '53 Chevy project I just picked up, but I have no idea what type any of the fluids are currently in the car, so looking for a little advice.

Oil is changed out, brake fluid is next, and then coolant, and maybe trans fluid...

To my understanding, DOT 3 and 4 brake fluid are a gold/amber color, and DOT5 is typically purple. Therefore, based on the pic of the fluid in my car it should be 3 or 4? And that being the case, I can use whichever I decide to go with (3 or 4) to flush/bleed without compatibility concerns, right?

The coolant...its green. Should I go ahead and ***ume its an IAT? I have a lot of aluminum and I'd like to use a nitrate-free OAT (like Peak Long Life), so I would need to flush the whole system, correct? I wouldn't be able to get away with just draining/blowing out whatever I can? (Not trying to be lazy, just practical)

Trans fluid - I wasn't planning on swapping out the fluid, but there is a small leak at the pan, so if I need to address that at some point I might have to. It's a TH350. Honestly I haven't done any research on the matter yet...Anyone have any thoughts on the type I should use, compatibility concerns, etc? I think Dextron 3 is a common fluid for this trans so I'd probably want to go with that.
(Pic is of brake fluid)

 

spray some spray paint on a bit of cardboard...let it dry....drip some brake fluid on it...if the paint crinkles, it's the good old kind

Dexron III/Mercon is probably the easiest to find fluid that will work fine in the TH350. Also be sure to look and find where the leaks are actually coming from, it's usually one of about a dozen leak prone areas on that transmission...shift shaft seal, dipstick O ring, speedo sleeve O ring or inner seal, kickdown cable or O ring, ac***ulator cover o ring, pump gasket or O ring or washers or seal, etc. ad nauseum.

 

Whenever I purchase a used vehicle, I change all the fluids no matter what.
IMO if your dealing with a stock motor, just the basics when it comes to fluids.
That brake fluid doesn't look bad, but I would replace it just to know it's clean.
Looks like you're on the right track. Have fun and drive the hell out of it.

 

Its got a mild 350 in it, so not stock but not a monster.

I agree - even if fluids look good I think its still best to start with fresh and know where everything is in its life. I suspect its all pretty old anyway based on what I know about the cars history.