If this is a stock motor I do not think it will like 20 initial and how fast the rest comes in can cause issues.

Also do not confuse mid rpm cruise with low load (partial vacuum) and high advance as compared to full RPM and heavy load (no vacuum). Total advance is debatable but in the 32-36 range under load. Cruise will be higher. A hemi typically a little less than a 440.

Should gap the points and check dwell individually. Both need to be in spec. Then total should be higher.

A non emissions hemi in 67 used 12.5Deg initial. Had 15-19 mechanical crank advance by 2800 RPM, and would give 0 degrees vacuum advance up to 9" vacuums in stock configuration. That is a total of about 32 degrees drag racing your buddy on Friday night.

A emission hemi in 68/69 had 0 initial and got 32 degrees mechanical at crank out of distributor at 3100 rpm. Same vacuum curve.

Depending what parts have been mixed you should get the distributor curved to ensure it is doing what you think. You can then play with initial. Vacuum advance for stock can is 0 at 6-9"; 9-15deg at 12" and 16.5-22 degrees at 15" (light load idle)

Your probably getting 40 plus at pretty low rpm which is not doing what a hemi wants. IMHO