Have 100 less hp?
I'm not saying a 383 can't run but if you ever looked at the bottom of a 4.25" bore with 2.14/1.81 valves compared to a 400 block you will quickly see why the 383 has been set aside for stock type builds and restorations. The hopped up 383 is like Foghat. It went out of style in 1978 but it's still on tour lol.
The bore and stroke are for the most part arbitrary when comparing these two engines considering the BBM has a 15 degree valve angle and the SBC 23. That is where the power is going to be made up.
