Forgive my ignorance re brake fluid

[Wrench29]

I am working on the badly neglected, brakes this weekend. I have my replacement parts (via Ebay in Argentina) and am ready to go. What type or grade of brake fluid is compatible?

[Rusty]

I just use plain old DOT 3 brake fluid .   Cheap and very common and easy to bleed.  I change the fluid in my old cars every few years.  They get water in the line from moisture in the air and degrades the fluid and can cause rust in the system.  The brake line on these Plymouth were originally copper so rust is not a problem.
Dot 5 is silicone and is not comparable with dot 3.  The advantage of dot 5 is that it does not absorb water.  A pain to bleed since it is very easy to get air bubbles in the system and then very hard to get them out.
Stick with dot 3 fluid.  I would say most old car people have dot 3 in their babies.
My two cents.
White post restorations recommend dot3 over dot 5 and they do a lot of brake rebuilding and restoration .  That is what they told me when I had my hydrovac rebuilt by them (. 1941 Chevy fire truck )
Rusty

Also, dot 3 eats paint, do not spill any on painted surface.  This is why most old master cylinders are so rusty.
I had my 29 master cylinder and wheel cylinder all bored out and sleeved in stainless.  They were too heavily pitted to just do a simple hone and rebuild.

[Tinkeys]

I agree with Rusty did my 30U and 34 Dodge with dot 3 and no problems  in Australia it's recommended to replace fluid every 2 years  !
I have used silicone years ago and brake pedal always felt like it was spongy ! So now I reverted back to dot 3
Cheers Tony.

[Wrench29]

Thank you both SO much for your information.  My instruction manual said to purchase Plymouth brake fluid at my local Plymouth service station. Ha ha.

[mopardave]

I went the silicon route for a while, but I had problems with it so I am back to good old DOT 3 and just rebuilding every 5-8 years.

[Rusty]

On my other stuff, most of my wheel cylinders and master are all sleeved in stainless or brass. I have not rebuilt any brake system (a second time) since doing such.  It does geta little old having to rebleed brakes every few years.  My main problem is my helper is not so much help.
rusty