66 Valiant 6 to V8

Those Kelsey/Hayes small bolt discs are good brakes- I would wait until you locate a rear end before you change anything. If what you get is a small bolt 8.75, I'd just stay with your current front discs. If you score a large pattern A body 8.25 (or BBP 8.75), then I'd change to the big bolt front discs. That way your bolt pattern stays consistent front and rear.