96 Lumina Low Coolant/overheating driving me crazy

Just (trying) to finish up this LIM gasket job on a 96 Lumina 3100 motor, thought I had the system all bled out and all, but when it actually runs (drives, road test) the SOB throws a low coolant light
and eventually gets up to a hot light being on. Let me be clear here, I have replaced:
LIM gaskets UIM gaskets fuel injector o-rings every single coolant hose under the hood water pump thermostat (tested before install) power-flushed out the radiator, flowed 100% clean with a pressure washer (straight water, no chem, did a radiator swap too, didn't help) heater core
Been trying to bleed out the system (with heat on high and blower on 1). What seems to be happening is the coolant is backing up into the overfill reservoir, as if there's some sort of restriction somewhere or air is somehow getting into the system?
I'm about ready to put bullet in this thing and put it out of its misery, unless someone has some suggestions for me. Thanks.
-GV
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Did you bleed it using the bleeder screws on thermostat housing and the pipe above the wp? That's all I can think of unless it's head gaskets.

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Yes and yes. Car isn't exhibiting any signs of head gaskets, no white smoke from exhaust, no leaks we can find, oil is clean, etc.
-GV
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A bad head gasket can pressurize the system blocking circulation but not leak back into the cylinders, unusual type of failure but it can happen. If it is air bound, try jacking up the car in the front and letting it sit o/n with the cap off, also try bleeding it this way hot also.

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o/n ?
Don't really have a good flat surface to play on, the street is pretty slanted, would it help to be doing this with the nose facing "up" the hill instead of down?
-GV
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