I have this table from Alice. It's an excellent substitution list since higher % have
more fat and WILL affect the outcome.
Here's the concept: higher % chocolates (ex: 70%) have more fat/ less sugar than lower % (ex: 53%). If the recipe calls for a higher percentage, but you have a lower one available, you need to add fat and reduce the sugar called for in the recipe. That is the brilliance of Alice's table.
You won't have an exact replacement but the science behind the recipe will work.