If everything was exact engine wise between the 383 and the 440, I would expect about a .5 better ET too.

But the 383 has .7 more comp then the 440, Theres 2 tenths IMO from that .5

The Torker II intake is a dog below 4500, some will say 6000 rpm. theres another 1.5 tenth with that 3500 vert your buds using.

Also, as you already found out, the exhaust is not guite up to the task with the extra cubes.

IMO, the above added into the combo, plus the Extra weight of the 440 kept the ETs around the same between the 383 vs 440.

The fix, Swap out that Torker II for a RPM.
Throw on a steel shim to gain some comp. back.
Upgrade the current exhaust as you have planned.

Then you will have your .5 gain or better IMO,

The 111 MPH of the new combo suggests sub 12,s as is with just a Vert swap alone. Id do that later after fine tuning what you have now.