What size spacer best for heat soak slant 6 Carter

I am having issues with hot start on my 63 dart with a 170 slant 6. I am guessing it's heat soak. Cold start is good. Once running it's good. If you start it right away after shot of it's good too. It's only really an issue if it sits 5 minutes or more after shut off when warm.

All my reading leads me to think it's heat soak. Running regular gas right now.

I am thinking of trying a carb spacer to see if it helps. What thickness is best? 1/4" or 1/2"? Also can someone tell me what the bore size and bolt spacing is for the Carter carb on a 170 slant six? If my research is right I'm thinking 1.70 center bore with 2.95 or 2 15/16" center to center. Is this correct?

Thanks in advance