Pictures would help and more info on Distributor. Assuming electronic and not points? Since you had or built the motor, it would be worth the effort to look in the service manual and take apart your distributor to check it out. The Cam stop will probably have a number stamped on for your mechanical advance. You may also have one stamped on the arm of the vacuum. As stated modern original MOPAR distributors had 24 to 30 degree mechanical advance, and Initial was set around 0 degree give or take a few degrees depending on motor and transmission. Roberts advice of keeping total without vacuum advance under 35 until you sort out the combination is smart advice.
