Mpg on a mild 360?

So I'm kicking around the idea of driving my dart to the nats for the first time. It's about a 200 mile trip and I'm trying to figure out the gas budget. I honestly have no clue what mileage I am getting because I usually am just on back roads with the pedal to the floor. I'm trying to get a estimate on highway mpg though. My combo is:

360 .30 over
Eddie heads
Mp. .484 cam
Performer rpm intake
Hooker headers
727 with 3000 rpm stall
3:55 gears

I was thinking using my Eddie avs 650 would help but I also have a Holley 750 dp.

I'm sure I'm not the only one with this combo or a similiar one so what are others getting for mpg?