I find this thread interesting too (and sorry if I helped it veer off) it all applies to all AMC motors.
'lugging' it is not a good idea.
generally, your engine will be most efficient near its torque peak. if you want great highway mileage, you want a cam that moves that peak down toward your highway rpm.
As I see it, there's three things in tension: lower RPMs keeps frictional losses low, but you must have enough to makde decent torque and HP. 1600 rpm sounds great, but it's impractical to make HP there. 2000 - 2500 is probably a good target RPM for torque peak, probably line up all the hard parts (trans/OD/axle/tires) then have a cam ground to put it spot on the target RPM/MPH.
But first you can take really big hints from what the factory did; little americans with manual trans and steep axles, see where those cams are ground and start there.
Somewhere I made a big table of all the AMC six cam factory grinds (60's - 70's) but I can't find it!