If I remember correctly the Walker exhaust catalog of 40 years ago listed the same headpipes for both 383 and 440 dual exhaust applications. Obviously there is a difference in the position of the manifold flange between the two.

Somebody check my math but if the 440 deck is .750 taller that would place the headpipe flange about a half inch higher and a half inch closer to the fenderwells than on the 383 – assuming identical HP manifolds for both engines.

Given that difference I assume the OEM headpipes were different between the two engines? I know some 440’s had H-pipes which would make them different but I’m just asking about standard dual exhaust

B & E bodies The difference is a 440 HP used an H pipe and a 383 HP had individual head pipes.

67 different manifolds between the 440/383 engines
68-71 same manifolds 440/383

All my stock '68 440s had H-pipes, my stock 383s individual pipes.
'68-'69 manifolds are essentially the same at the manifold/pipe flange, but the rt side '70 flange is clocked differently.

So is it likely that in the 68-71 era all 440's with HP manifolds had H-pipes from the factory?