What to do with wiring?

[Clutch1819]

I have a 90 c1500 that had the 4.3 tbi engine. Currently in the process of putting a carbed 350 in it. Can I use the factory engine harness for the 4.3 to run the oem gauges or do I need to scrap it and use aftermarket gauges? The plan was to use the in tank fuel pump with a holley bypass style fuel regulator. I need some opinions....

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