Just swapped my 99 GT with an 04 p71 motor, made sure all the under hood grounds were solid. Weird issue is that I had dash lights after the first start but lost them after hooking up my belt. They used to be on 24/7 when the car was running, they never turned off but they still dimmed whenever the headlamps went on. But now they don’t come on at all, checked all the fuses for instrument cluster, no dice. Tbh electrical is not my strong suit, the car in question did have aftermarket gauges...

99 GT dash lights inop