Ignition woes - switch needed?

[GMCNUT]

I don't know why, but when its cold or started for the first time, my 72 blazer ignition has started hanging when I hit the key and the starter will turn over and over and over a thousand times unless the motor starts or I disco the battery. When hot, its started deciding not to crank at all - flip the switch and nothing happens like its totally disconnected from power. After it cools down, seems to start fine. Assumed at first this was a starter solenoid issue, so I replaced that with a brand new one only to see it act the very same. So turned my attention to the ignition switch and replaced it with a same switch spare I had laying around from a junk yard truck, and it is still doing the same thing. So I assume the junkyard ignition switch was as bad as the one I swapped it out with? New solenoid? Can't be the starter itself I would't think because it waits for the ignition to be turned on to make the solenoid jump out - the solenoid would work regardless of the starter working and thats not occurring so it has to be the switch itself - right?
So, assuming all of you agree the switch must be as bad as the one I removed, Ebay shows about 10 different ignition switches and each seller claims their switch is correct for 67-72 - part numbers I see are:
1116695, 1116704, 1116688, 1116711 and on and on. Does anyone really know what GM part # the ignition switch is supposed to be for a 72 Blazer w/ normal 350 V8 / Automatic / CST / etc?