for the carter guys... jetting and other q's

Hey Guys,
Just picked up an old AFB #9626SA for my Dart. $25. Clean as a whistle inside and out (had it apart to check everything). Guy had it on his Lil'RedTruck.
Was wondering what ballpark jetting/metering rod set-up should be to go on my bone stock '78 318 in my '71 Dart. Edelbrock Streetmaster 318 manifold, 2-1/4" duals on stock manifolds. How about with headers and maybe a Comp Cams XE256H? Just looking to pep up the teen a little.
On another note, being new to this stuff (Cars that is,I wrench motorcycles full-time),I have to ask; I noticed behind the Fast Idle Cam there is kind of an upside-down T-shaped piece that swings loosely when the choke is closed or partway closed,preventing fully opening the throttles, though when choke is pulled off the Fast Idle Cam holds it out of the way... At least that's the way I see it. Am I correct in that assumption? Or does it do something else?
Any response appreciated ( I figure that someone else has run this combo in the last 35years, why not ask and listen...).