Timing question

Distributor timing will mechanically advance with rpm, normal.
Disconnect and plug vacuum advance hose..then get the carb off the choke... then adjust the distributor counter clockwise till you see about 12 degrees advance at the tab/balancer and tighten it 'for now'...then.. hook up the vacuum advance and check the timing with the rpms around 4000...and see how much the vacuum advance adds.
You really dont want more than 52 degrees total @4000 rpm. If it's more than 52 you can adjust it with a allen wrench through the canister nipple...
Remember ....the vac advance only cones into play at high vacuum 'cruise speeds' otherwise the timing will be on the mechanical advance under power/load.

Most sb dodge distributors have about 24 degrees mechanical advance , that's about 36 total if set at 12 btc degrees initial/idle.