Set the idle down a bit on the roadster. It's spooky how slow, and quiet this is at idle. https://www.facebook.com/video.php?v=593966795809791
I don't know, I don't have a dwell meter any longer, so, like all my "tuning", I just go by ear. It's pretty slow, but doesn't stall at idle or stumble accelerating, seems good to me.
Make sure it is making sufficient oil pressure at the low idle speed. At very low RPM the pump will struggle to work properly. That's not good..........
I believe the Desotos were known for there very smooth and low idle. They used a very wide lobe separation. Assuming you have a stock cam. Yours sounds great.
I like slow idles. My olds holds about 650 at idle, my flathead is 600-800 rpm (depending on the Stromberg's at any given moment), my stupid dune buggy idles at 1100 and is annoying but I haven't had time to mess with it. Fast enough to oil the top end.
I had a 241 Dodge hemi. It didn't make enough noise to know is was there. It also made about the same amount of power.