Carb and tuning issues with new headers

5 degrees is not nearly enough intial timing for one thing. You need to get the timing set up for your combo before you can worry about getting the carb dialed in.

The amount of intial timing is a function of the cam and how much over lap it has. The more overlap the more timing. Don't be suprised if you need to have the initial timing set to as much as 20 degrees BTDC. My hot 360 is happiest at 15 degrees BTDC with a Comp XE268H cam which has a fairly wide lob spacing that reduces the overlap that a more typical 268/280 advertised duration cam has.

With an idle vacuum of 5-6 "Hg you either need a ton more timing or the cam is very big. You adjust the initial timing by advancing the timing in 1 or 2 degree increments while maintaining the idle rpm until you get max manifold vacuum.

NOTE: if you are much beyond the factory 10 degrees you will need to limit the total mechnical advance in the disributor to around 35 degrees. Stock distributors require welding slots, after market such as the MP distributor have adjustable limits for mechanical.

Also, something is wrong with the carb if you have fuel dribbling out.