1972 coolant temp issue

[1957belair409]

Ok I have a 1972 Jimmy I'm working on building. It has a TBI 454, 1993 era. Everything is new or rebuilt. I just installed a restored factory tach vacumn gauge cluster. Before I removed the old cluster I noticed the water temp gauge was barely moving when the engine was at full operating temp. It will move up about the thickness of the needle, so not quite past where cold starts. After installing the rebuilt cluster, I noticed the different gauge was still not working. I went and bought a one wire sending unit from Oreilys and got it for a 1972 Jimmy. I have it screwed into the top of the waterpump next to the heater hose port. That must be a newer design I guess. Still no change. At some point while working under the dash, the gauge shot all the way to hot, maxed out. I understood from what I read on this forum that I had a bad ground. I have a temporary wire ran from the bottom terminal of the gauge to ground and that has fixed that problem. The original cluster to the truck has a resistor with a blue sticker and my rebuilt cluster has a resistor with a red sticker!!?? Also ive seen pictures of gauges from this erra with a yellow sticker. i know this has to do with ohms of resistance. which one woud be stock? I've also tried adding 12 volts to the far drivers side terminal of the temp gauge per an illustration I found online. Anyways, I'm about to say hell with it and mount an auto meter gauge in the glove box. Has anyone ever had this issue?? I'm baffled. Ow ya, I have one of those heat guns with the lazor and when my electric fan comes on, I'm showing 160 at the water temp sensor. That's not really super warm but should be more than enough to move the gauge into operating temp I would think. I have a 1971 Cheyenne and it has the blue resistor. Never had an issue. Any info or input will be happily read. Thanks.