This is the roof rack that I'm using for the 1/12 scale 1972 Chevy Prerunner build. Youtube playlist link: https://www.youtube.com/watch?v=qmpR-BLqDcM&list=PL_C9a338X9XNPDtQkikr2Rt29hYTUveQI
It is specifically designed to fit the Pro-Line 72 Chevy C10 body, however this could easily fit many different bodies.
Two options for this are available, a one piece roof rack and a split roof rack which provides a flat surface to make printing easier.
The lights were designed to be printed on an SLA printer, so printing them on a standard FDM printer may be difficult.
Things you will need to complete the roof rack:
4 M1.6x5mm screws.
Thin plastic for the lenses (less than 0.4mm thick cut to around 11mm in diameter)
4 3mm LEDs for the light buckets
Wires for LEDs
You can see this roof rack being assembled and painted in this video: (skip to 18:42) https://www.youtube.com/watch?v=0WvZfSTp3Q4