Right, ace. Six degrees is the right amount of vacuum advance for any engine in any car, from a '60 Valiant with a 170/3-speed and 3.55s to a '73 Imperial with a 440/automatic and 2.71s to a '79 Aspen with a 225/4-speed overdrive and 3.23s. You betchya. So Chrysler (and, um, every other automaker) wasted alllllll that money making allllll those different vacuum advances giving alllll those different amounts of advance. Instead they shoulda listened to Six Degrees Guy on the internet, 'cause he knows that six degrees is the right amount of vacuum advance, period. You betchya. Are you even listening to yourself?
By the way, dude: of all the Slant-6 vacuum advance units made over the years, none of them is a six-degree unit. All of them give at least ten degrees, and some of them give a whole lot more than that. If you wanna know why, go study up on why vacuum advance exists and what it does. It won't take you long to learn; I recommend
Auto Mechanics Fundamentals by Stockel & Stockel.
While you're doing that (or continuing to sit there insisting you're right and the automakers and the entire rest of the world are all wrong), we'll be over here helping the OP get his Dart running well.