Cluster problems, really need advice

[74chevylvr]

Need advice:. On my 74 swapped in a full harness from a 78. Swapped the oil sender for an electric one, swapped the temp sensor. The cluster is from a 79. Circuit board looks good.

The only thing that works on the cluster is the gas gauge, the fasten seat belt buzzer and the left hand turn light. Nothing else.

I really don't want to spend hundreds just throwing gauges at the problem

Any advice? All of the light bulbs are in, however only the left indicator light works