5 volt resistor for gauges

Yours, as you say, does not plug in. You must "safe" disable the old one and wire it in, mount it on the rear of the cluster.

Here is some info

There may be other methods and other sites, do a search

https://www.rt-eng.com/index.php/RTE_Limiter2_Faq.html
There are 3 terminals on the fuel gauge as opposed to 2 on non-Ralley clusters. One terminal is fed switched 12V from the key, goes into the gauge housing and operates the limiter. The limiter internally feeds the fuel gauge as well as bringing the 5V out to a stud to jumper that power to the other gauges. The third stud is the sender

When you wire in the new one, you rob 12V off the proper stud, and feed the new IVR to the 5V stud on the gauge.