[FUNFER2]

I can't believe you're getting that low of mpg, with such a mild 390 ?

My last 428 was fairly mild, but higher than yours.

10.3 compression.
.060 over bore.
600 lift, 252-260 duration.
650 Mighty Demon carb.

16 mpg highway.
(no info on the street)

It at one time was around 11-12 mpg.
For the Hot Rod Power Tour, we ran it on the chassis dyno and went down 3 pill sizes, could have been 4 but, he did not have that jet.

I highly,......recommend putting it on a chassis dyno and see if you can adjust the fuel curve by going down on the jet size. It saved me a lot,.... of fuel.