I have a 327 with a Quadrajet carb that I built, hoping that I would be able to get optimal fuel economy and use 87 octane gas.
I have a 700R4 transmission behind that.
This engine has pretty low compression at 8.5:1 using 76cc smog heads with flat top pistons .040" piston crown to head clearance.
This combo falls short of my expectations, however, as far as fuel consumption goes, because it is geared too high to pull overdrive with the TCC lockup engaged.
When I run with the trans in OD the vacuum ga is at about 16 - Then when I engage the TCC switch, the vac gauge drops to about 11.
This is not good for economy - It starts getting into the power system of the Q jet.

The heads that I am using are 76cc with 1.94 / 1.5 valves
I am sure that raising the compression wouldn't hurt so I got some Dart Iron heads with 72cc chambers. This will give me about 9:1 CR
The heads have 2.02 / 1.6 valves.

I have noticed that the combo I have in there now begins to wake up at 1800 rpm - and above that the engine is more responsive and the vacuum gauge doesn't drop as much with pedal travel.
The thing that I have going on is that when I am cruising at 60 I am at about 1900 rpm in OD with the TCC disengaged.. When I engage the TCC it drops to about 1700 rpm, which is below the rpm where the engine is happy.
The engine actually cruises at 70-75 using less vacuum than it does at 60 - But 70 - 75 will get me tickets
At 60 I am right on the edge of the engine's operating range

If anyone has any suggestions or comments on this, I'm interested in hearing

I've thought of changing my gearing, or tire size to put it more into the operating range of this combo, But I'm planning on swapping heads first

Thanks in advance - As Always

 

I am no expert at this stuff, but it seems to me your simplest solution is changing gear ratios. If you like how it runs now, dropping the gear ratio (numerically higher) will give you slightly better acceleration and bring the 60mph rpm up to the ideal range for cruising at that speed. Maybe just use an online ratio/rpm calculator to find your new ratio.

My 1985 camaro gets its best mileage (about 22mpg) at 70-75. This doesn't need to turn into a thread with everyone boasting their alleged mpg's, but I would be surprised if you get much better than that, especially limiting your speed to around 60mph. Whatever the variables are, best fuel economy boils down to propelling the car as fast as possible in its most efficient rpm range.