A 'small' big block most likely had 10" drums on it. On this 5.9 engine, is the distributor at the front? If so, it's a 361.
And soft shoes generally means fade on hard stops. I ran the 'better' 11" drums on all 4 corners on my old 10.60 car and had no problem stopping hard but usually let it coast down and used the brakes easily but I knew if I had to jump on them hard, I could and this way, the drums lasted a long time. If one is easy on the brakes, the 'hard' stuff won't cut your drums down and you don't have to worry about fast fade if you ever have to 'use' them hard.