Advice Needed - Can't Start Rebuilt 273

Final Saturday update:

Got it to start - sort of. After a lot of cranking and tweaking, it caught briefly a couple of times but wouldn't keep running. After it did try to run, it then wouldn't fire off again without a lot of cranking. When it did "run", it was pretty rough - probably because it still wasn't running on all 8 cylinders. I have quit for the day - battery is used up.

Any suggestions what I can try next? I have another known good carb from a 360 I will try on it.

My other small blocks have Champion N12YC plugs. Is this correct for a '66 273?

Also, I'm using the old Mopar starter which seems to turn it over quite slowly. I do have a mini starter I could use. Will it crank it over faster?

Thanks for any suggestions.