most hp from std block
What Leon said.
I've had two early 70's 360 blocks in two different race cars. One, about a 400 horse bracket motor, has been in the car for thirteen years, probably has 1500 passes on it.
The other has, my guess, 500 runs in 5 years, with about 550 horses. It's not hard blocked ( it needs coolant passages down here, it's HOT!).
My machinest is a Chevy guy, but praises the early 360's as a very tough, well made, with lots of "good" metal in the casting.