Got the second Stant 170° stat at O'Reilly today and installed both as follows:
First tested them to make sure they worked.
Here they are first opening at 160°
And fully open at 180°
Then drilled 3/32" hole in the flange to allow air to escape when filling. (Would have drilled 1/16" hole but broke the bit

) Tried to get the jiggle plugs from my other stats to work in these holes but they wouldn't.
Sat the stats on the neck with their gaskets on them to see how they fit. The gaskets extended slightly past the neck so I thought they might be well to leave on to keep the stat from "floating" up as they like to do.
But, still didn't want to rely on the gaskets alone so installed my usual wires to keep the stats down.
Got a piece of 12 ga. stranded wire 3½" long and stripped the two ends to make it easier to pull strands out.
Then threaded the wires through the stat and down the side of the neck to be held down by the hose.
Then put the hoses on, clamped them down, and filled with water to test for leaks. Could not get the water to stop leaking under the hoses. Took them off and discovered that when I pushed the hose down over the gaskets on the stats it rolled the gaskets off the stats and down around the hose preventing them from sealing. So, removed the gaskets and reinstalled the stats without them.
The stats are just slightly smaller in diameter than the necks so the hose alone would not keep them down without the wires or a second clamp around the hose above them.
Gotta use the small strands of stranded wire or the hose won't seal around them. The clamp should be installed so that the top of it is even with the top of the neck, not lower as the neck starts to flare lower and it's harder to get it to seal.
Filled the radiator with soft water and two bottles of Hy-per Lube Super Coolant up to where it ran out of the overflow just to see how much pushed out when it heated up so I could report what the nominal level of water in a stock radiator without a recovery tank is.
Checked for leaks again, found none, and was ready for the second climb up Squaw Peak Road to measure temperatures with the thermostats in. (That run is done and report of such is being prepared for posting.)
Addendum: After the run I measured the level of water in the radiator. It was 1½" below the top of the filler neck which is the highest level that the stock radiator without a recovery system will hold.