Dilbert,
I tried the car-push a number of times.
Some of my other cars move real easy, but the Dart takes some effort to get rolling.
I've always found cars are a bit harder to push backwards. Probably because more internal transmission parts are being rotated then I think.
The 3.55 gears make it a tad harder too, but that should work opposite when power is coming from the driveshaft.

Transmission has ATF-4, external cooler in front of radiator. But transmission oil never gets really 'hot' so installing thermostat would be better I think.

I ran with 0w20 synthetic oil in the 318 during the last year or two.
Besides easier acceleration during morning starts it had maybe a very slight noticable effect otherwise.

Thought about putting synthetic oil in the (Auburn SG) diff. Or maybe even a thinner oil, but I that would focussing on .1 of mileage numbers I would think.

Car has cold air intake.

Ignition timing is digital (MegaSquirt) and I have been tuning the timing map for quite a while now. Timing is increasing the moment there is little to no load on the engine.