MPG The Best Of Both Worlds

Car-1969 DART GT
Weight-3300
Gear ratio-3.91
Tire diameter-245/60/15
Engine CID-365
Head Type-EDELBROCK
Valve size-2.02 1.60
Head Work- MILD PORT
Cam- Comp Cams 20-225-4
284 int./296 exh.Carb type and size-HOLLEY 4150HP DP
Jet sizes-74-78
Plug number and brand
Intake Manifold Type-RPM AIR GAP
Piston Make-SPEED PRO 4 VALVE RELIEF
Compression Ratio-9-1

Trans type-727
Trans Mods-MANUAL VALVE BODY
Convertor type-MIDWEST CONVERTER
Convertor stall-2800
Trans Brake-no

Drive shaft stock or aftermarket-STOCK

Initial timing-17
Total timing-35
Total advance at what RPM-2000

Rear end type-8 3/4 3.91 suregrip, single spline side gears, yukon axles,green bearings.



What would be the best mods to up the MPG without sacrificing E/T to much.
Here is what I have.
Sell 360...400 big block that needs a rebuild in the garage ( more power at less rpm)

Edelbrock 750 vac sec carb. 3.23 gears (came stock with suregrip)

I have an appointment to get the Dart dyno tuned June 4. Want to get the best tune possible.

Swap carb and gears, buy a new cam?
Keep carb, cam, swap gears
Keep everything the same, tune