Hi justinm go to http://home.rmci.net/blueskies/plymouth.htm for a look at a car with a modified stock manifold (he removed the heat riser, however) and dual holley 2 bbl carbs. You may get a reply from the owner of that site here, since I learned about it from this forum.
I have my dist. advance connected only to front carb of my dual B&B setup. There is no fitting for vacuum on the rear carb.
An outfit called The Carburetor Shop can help with parts for your carbs. I found them doing a web search, but I don't remember the URL. The plymouth site listed above may have a link to them.
If your offy manifold has a provision to use the heat riser on a stock exhaust manifold, you could preserve it by just adding a 2nd oulet pipe to the front half of the manifold. This wouldn't really be a split manifold, but I've seen it done, and it works ok for getting a nice sounding dual exhaust system, even if it doesn't provide the performance boost of a true split header.

[This message has been edited by carlo (edited 10-31-2001).]

[This message has been edited by carlo (edited 10-31-2001).]