super six advise and questions

my dart has a mostly stock rebuilt /6 from a 68 fish. i have a cast super 6 intake. i dont have any of the other oe parts to the super 6 but do have a couple 2 bbl carbs laying around. how much carb is to much? is it better to just find a bbd?
I have a holley 2 bbl from a 360.
a holley 500 2 bbl
a Demon 500 2 bbl

I'd take it from the 360. From what I've been reading 500 might be a bit to much. Most are sticking 400 and maybe a bit lower. Unless you are modified and your post doesn't seem so.

All of the carbs you have are (way) too much/too big. A 273 or 318 carb (Carter BBD or Bendix-Stromburg WW3) can be made to work well with some adaptation and adjustment. A BBD originally configured for Slant-6 usage is the easiest and generally best-running factory carb option. The hard part is finding one in good condition, which means avoiding "remanufactured" junk and "100% NEW NEW NEW NEW!!!!!!!1111!!!!!" knockoff garbage from China that's all over the internet. I have another one (last one) of these on the shelf in Michigan; send me a PM if you're interested.

If you want to explore non-factory carb options, the Motorcraft 2100/2105 has been adapted with very good results; see this thread and this one.

If you have an automatic trans, you'll need a different kickdown linkage. Factory parts have grown scarce and expensive; See this thread for kickdown options.

You'll need an air cleaner -- a factory-type unit is best; which one to get depends on which carb you'll be running.