Is the 383 a better engine, or does the 440 just have more displacement?
I used to be able to shift me 170" 6 cyl 3 speed 63 econoline van without the clutch.
Run engine up to the right speed / rpm and gently move the shifter from 1 to 2 or 2 to 3 while keeping the engine rpm at the correct speed for the gear.
It was always a gamble but 9 times out of 10 it went ok.