Vacuum advance tuning to maximize cruise MPG?

My motor likes a lot of initial timing with a fast curve. I did not build this motor it cam with the car and is #s matching. I crudely degreed the cam using a dial indicator and readings off the crank. It's around 270 duration and has .435 lift at the valves. I check the timing chain by watching the rotor as I rotated the motor CW, then CCW and the chain is not worn out. The motor starts to make real power around 2300 and I suspect it has a cheater cam in it.
I've thought about swapping in another cam, but decided to tune what I have. I have a 67 Dart that is almost done for a drag car so the Dart Sport is my DD cruiser.

I'm running full manifold vacuum, engine idles in Neutral and Drive at 700 rpm 15" Vac

All timing #s are at the crankshaft
Initial mechanical at idle 24* + 14* mechanical = 38* total mechanical, all in by 2200 RPM
Vacuum advance 22* @ 15"

With vacuum advance connected at idle 24*I+22V* = 46*
With vacuum advance connected at and above 2200 rpm 38*TM+22*V = 60*

Yesterday I did not have Vacuum can setup right so I pulled it off this morning and grouund the mechanical stop. Put it back in and know have 28*V at the crank in max allen screw adjust.

The motor did not like it and I kept decreasing the adjustment and rechecking with my Mighty Vac pump, and settled at 22*V@15"

As AJ mentioned I did have to tune the can to 15" to keep my initial timing bumped up at idle since I'm using full manifold vacuum as my source.

After getting the vacuum advance set to 22*V I had to reset the idle air fuel ratio and primary mixture screw on the TQ tree. With the wideband it's a piece of cake.

Took it for a ride an gained an 1.5" vacuum at highway cruise. I also took AJs advice and watch the vacuum gauge peak at 2500 rpm. The motor is putting out more torque and I felt it during the up shifts. My trans has a TF2 shift kit and does not slip; I took 1 turn out of the throttle valve linkage.

I think I'm dead nuts on or very close to a good street car tune. When I get the MSD timing box I'll do the adjusting from the dash and watch for the MPH change.