Has anyone ditched the 4 headlight grill for the 2 round headlight grill? Are the core supports the same? Can the headlight harness be swapped? Any other pitfalls?

Thanks

The core supports should be the same except for the headlight buck area. But you can adapt that. Be cheaper than trying to find a good two headlight support. I swapped my '81 over to '72 grill and sheetmetal, and kept the '81 support. Wiring should be ok to use, just use the headlight plugs for the hi/low beam lights.

The quad lights have a little harness that plugs into the standard truck light harness so good there.
Adapting the round H/L buckets to the quad core support is the biggest set back.

It irks me to see the wrong grill in a specific year. But you can do what you want. I got the best looking year(in my opinion) a 1978. 79 used both the single and duel rectangular lights.

If you're trying to go from 79/80 stacked headlights to round the only difference is the headlight buckets and the headlight pigtail. It's easier to go the other way.
If you're going from that to the 77/78 grille there are more differences but the hardest is probably going to be the headlight buckets.
You also end up with a second set of turn signals unless you do more work.

Thanks for the info

I would think finding a good '79/'80 grille will be the hardest part. I have a large shelf full of '72-'78 grilles but only 1 or 2 of the '79/'80 round headlight ones and I've been collecting them for like 30 years!