B-52H:
Payload - 70,000 pounds
Speed - 650 mph (Mach 0.84)
Inventory (2013) – 78
B-2
Payload - 40,000 pounds
Speed - 630 mph (Mach 0.95)
Inventory (2014) – 19
B-1B:
Payload - 75,000 pounds (125,000 w/ externals)
Speed – 900+ mph (Mach 1.2)
Inventory (2012) – 66
IIRC older models B52s carried MUCH more than this over Vietnam. We basically flew the wings off those models. The base design was modified differently than the models we’ve kept.