distributor vacuum advance

I think I need a new vacuum advance unit and was looking for some input on which one to use. My car is converted to the Super six setup and I wanted to know if I should change the vac advance over to the Super six one. Right now my distributor is the stock 198 with petronix and a 225 vac advance from a 69 slant (is there a difference in year/motor?) Also the parts store lists 2 different options for vac adv for a (1978) super six anyone with a part number would help. Would the Super six cars having electronic ignition be a different advance? Thanks. :)