According to the CPP catalogue they recommend replacing the bearings but it should work with the early bearings as well. Since this kit uses your existing hubs there shouldn't be any reason they won't mount in the same manner as the stock hub/drum on your spindle. You are correct that their instructions are lacking in detail. Go back and check your inner bearing race as it also acts as a spacer.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine