65 A Bodie fuel & temp gauge problems

Let's be clear..........fuel ga pegs with sender DIS connected?

You may HAVE to learn some electrical

1...Do you have a factory service manual? If not download the closest thing over at MyMopar.com, free. Also there, in zip form, are two page aftermarket diagrams which are drawn differently than OEM, and are sometimes easier to follow. They are not as detailed, omit some options, and do not correctly document connectors. But they ARE sometimes useful

2...The IVR for these cars is INSIDE the fuel gauge so BE CAREFUL and do not power it up more than a few seconds to test.

3...This page may help, it's about replacing the factory internal IVR with one similar to what the later cars use

https://www.rt-eng.com/index.php/RTE_Limiter2_Faq.html
4...Does the temp move if you ground the temp sender wire and turn on the key?

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I'm guessing the cluster will have to come out

First though, troubleshoot for a grounded (shorted) fuel sender wire. First, get into the left kick panel and separate the rear harness. That is the most likely stretch of cable that would short. Turn on the key, see if the gauge still pegs. Go back to the tank and with key off, apply an ohmeter / continuity checker to the sender wire. Should be open now. If not, and with the connector separated, somewhere it is shorted. Check the grommet through into the trunk, and check the area where the harness goes past the rear seat. If not, check the cable through the rocker panel area. Sharp metal, screws, etc.