80 ohms = no needle movement. 73 ohms should = empty hash mark. 34 ohms should get close to the 1/4 tank mark but,,, your model gauge, from 1/2 tank down, even with the OEM sender, never was very accurate. The same 73, 23,10 tester was still used. Looking for what 1/4 tank is on your gauge just because you have the tools to do it is really only for fun. I have to say, all the time wasted over 2 bad senders is ridiculous imo. Need to know,,, the wire terminal for the fuel gauge was a booted 90 similar to what you have at temp sender. Yes a hex nut with toothed washer works but DO NOT OVERTIGHTEN. Turn that studs and get a fuel leak and likely break the connection other end too.