Voltage Gauge

[Custom06]

We recently replaced the worn out 305 on my son's 86 SWB and after replacing it with a freshly rebuilt 350 our voltage gauge stopped working. We've checked all connections, grounds and still nothing. I don't see any loose connections or grounds anywhere. What are we missing or did the gauge just die. Before we did the swap my oil pressure gauge took a dump and need to be replaced. I thought it was the pressure switch but after replacing it, still not working. Any help would be appreciated.