Remember a thread sometime back about using the correct brake fluid but couldn"t find it back.I have a 66 chevelle with a new disc conversion and all rebuilt drums on the back.What fluid is the best to use? Dot3,Dot4??

Dot3

Use the search function, type in brake fluid and you will find a ton. There is a very lengthy thread titled something along the lines of "what brake fluid do you run", roughly 3 pages long. lots there.