Help me get better fuel mileage

[steves1967]

I know it's been said/asked a million times. But 9mpg on my 97 K3500 dually sucks- and it's even worse when I pull my travel trailer. The family and I are planning a 4000 mile trip this coming spring. If I could get 2-3 mpg better I'd be happy! The truck is all stock at this point. Here is what I was thinking:

Cowl hood- to reduce under hood temps
Shorty headers- ceramic coated to keep heat in
Some kind of new air intake
throttle body spacer
Swap out the factory cats for some high flow units
Royal purple trans and diff fluid
performance computer program (hypertech, etc.)

I thought about pulling the cats out all together- but I dont want any check engine lights popping up either...

Thanks for the help!