What MPG are you 340 guys getting?

I don't have a 340 but shouldn't be too different, here goes:

I drove to Louisville, CO and back a few weeks ago from Ogden UT. area. About 500 miles one way. I do this almost every year.
I'm keepin' it around 70 mph so I try to stay around 3000 RPM.
I have a 360 with 10.2 compression, Lunati Voodoo Roller cam, alum. heads and an Edel airgap intake. Topped with a 750 CFM Street Demon.
A999 Transmission and 3.21 rear diff gears (8 1/4 rear).
The tires are 25.7 in. diameter

I got between 11.5 and 14.5 mpg this time due to going in to 40 to 55+mph winds and as well as crosswinds.
Last year I got a best of almost 17.5 mpg with a favorable 40mph tailwind.
On calmer days I get between 15-16 mpg.

Few takeaways. I love that Street Demon carb, it's simple, and has some Thermoquad elements to it.
An OD transmission is definitely in the near future as I'm going to install an 8 3/4 rear with 3.55 gears soon.
I got an A500 (42RH) in my garage from a 1992 Dakota 2wd that I'm going to rebuild.
And yeah, I need to finish my aftermarket A/C install.