Since you bought an old hammer gun, you likely knew that it would require low pressure loads. So you either reload or have a plan to get low pressure loads, correct?

If you reload, why not just shorten the hulls? If you don't reload, you're going to have to locate low pressure loads anyway. There are not likely low pressure loads available in 2 3/4" anyway. You surely don't want to shoot SAAMI pressures in an old hammer gun.