Bugga bugga chugga bugga cruise

The easiest way to get a richer mixture at cruise in your case is to change the rods to .073 x .047 (Edelbrock 1456)
The 1406 is a really good carb once you got it tuned right.
There IS a difference between 1405 and 1406 but not THAT much, I've got both of them and I can tune the 1406 to run just as good as the 1405 on my 383HP
I use a wideband O2 sensor when I tune and that helps alot.