With the super six the easiest swaps are the Small (super six and 318) Carter BBD.
Next on the list is getting a Mr. Gasket #1937 adaptor kit and running a Holley 2300 (like you're listing), you also with the plenum top adaptor from a Pinto/Mustang 1974-early 80's can run the Holley 5200/Weber progressive two barrel...
This will take some 'tinkering' to get it to run right. I think the Holley 2305 would be a nice carb to run , but they've been discontinued now for quite a few years.
If your slant has a stock cam, don't go over a 350 cfm Holley 2300 if you're going that route. I'd almost say you can comb the local wrecking yards for a rebuilder, I have one I' have yet to try, but it's numbered 80179, and is a 350 cfm with annular boosters for better signal and fuel spreading...this would work great on a stock mill where these factors will help mileage and throttle response.
If you have the use of a drill press you can make up some other adaptors for the other 'flanges' (like the big BBD off of big blocks, the Holley 2210 off 400's, or 2245 off of 360's...) out of aluminum chunks from a local scrap yard
The 2300 is a good carb if you have spare jets, shooters, accelator pump cams, and some time to really fine tune it in. It'll get you in practice for the day you decide to try a Holley 4 barrel...
-D.Idiot
