Since my Dart goes on long trips on occasion I'll throw my combo out there.
Stock bottom end 5.9 with a 214/224-.512 lift cam on a 110 lobe center.
Edelbrock 600 cfm on an aluminum dual plane intake.
1-5/8 long tube headers
Thermostat controlled electric fan
42RH OD trans with a stage 2 shift kit
HEI ignition and vacuum advance used.
273 gears currently
25 mpg at 80mph on the hiway running high 14's/low 15's AFR at 2,100 RPM's
This plus lots of compression
Another key is how much power extraction your cam has. Teeners have about 120degrees. The 292/108 has about 102. TB's cam has about 113 . My Hughes 223/230/110 had about 108. 102 is terrible for fuel economy leaving a lot of heat and pressure still in the exiting exhaust. 120 is teenersville, and you can't get that amount on a performance FTH cam. 113 is up the middle and a reasonable number. By 108 (my 230/237/110 Hughes cam) fuel-economy is in the toilet at 2250rpm
Another key is the cruise rpm, if you end up cruising at a too-low rpm, you will put the intake into reversion, where it will be difficult to control the AFR.
And hardest of all is to give the engine the timing it wants at low rpm, and if you don't, she will be stuck operating in an inefficient mode. Which means you will have to use more pedal than necessary, compounding the other problems. The lowest possible rpm is not always the best solution
The nice thing about the 360 is you can go a little bigger on intake duration, before the bottom end goes soft, and the more compression you can run, the greater will be the efficiency, so the less throttle opening you need, to cruise with.
TB's combo is an excellent example of an all-round great street machine.
But keep in mind that the difference between 22 mpg and 15 mpg is just 21gallons per 1000 miles. So on a 3000 mile trip you will save 63 gallons. At $4.50 per gallon this comes to just $284 smackers..... so IMO you kindof have to keep your eye on the big picture; How much performance are you willing to sacrifice to save the 21 gallons per 1000miles.
If you got deep pockets I recommend aluminum heads tight-Q,and 185psi with something like a fast-rate 220 cam,and a two-chunk system; one hiway and one "other",lol. It only takes an hour and change,to swap pumpkins; otherwise overdrive is the way to go. The hiway pumpkin could be 2.94s to top out first gear at 60mph@~5600. the 2.94s would cruise at 65=~2400
The "other" could be 4.56s to hit 65@5600... now in second,lol. Or some other "other".
At this performance level, another option is an A999 with the ratios of 2.74-1.54-1.00 and a 2400 loc-up TC. With this trans you could run 2.76s for a lil
more first gear punch; 7.56 versus 7.20 with the A904, and the cruise would drop to 65=2230 which I like a lot. 2230 will allow you to run something like a 228/232/108 fast-rate cam and still get ~113* of power extraction. You can make a lot of power with this hi-compression combo, and a lotta torque, and a good amount of steady-state mpg.
And the bonus is that the aluminum heads at 185psi, on the hiway,will easily cruise on 87E10, for another significant cash savings.
Cruise ignition timing for 2230rpm will be difficult. Mine likes hi-50s*. So you are gonna need a timing computer of some kind, cuz without it, all you can get is about 40/45*.. This is easily 10-15* short, putting your piston that amount further down the bore before the peak cylinder pressure hits, which has now gone soft. This loss of pressure is a direct loss of torque, and so a direct loss of mpgs.
IIRC TB runs mid 50s on his combo. I run a dash-mounted, electronic, dial-back, timing gizmo from a long-defunct company,(I think); Jacob's Ignition. It has a range of 15*, which if I set the timing with the gizmo's dial centered, is a plus/minus of 7.5* .. So, just to throw some numbers out there; if your mechanical timing was 22* at 2230 and the Vcan got you 18 more, that's 40* . So the gizmo would have to make up the difference to whatever your combo likes. The trick is to remember to dial it back when you come off the hiway, else your power timing will be way too high. Which with the aluminum heads@185psi, my occasional forgetfulness hasn't seemed to hurt them. I finally made it a mental rule to always check the dial before going hammer-down. That seems to be working for me.
If you are not interested in that amount of power, then; iron heads will be fine, with a smaller cam. Just run the cylinder pressure up to about 160psi, with a tight-Q. You might have to run premium gas at WOT, but it will still cruise on 91 or 87 even. And the bonus is you won't have as much trouble with the timing curve.
Ok enough talk,lol.
