Are you referring to a complete dash, or just the gauge insert panel? I also made a gauge panel for my Falcon, as the speedo insert incorporated all the gauges and idiot lights, and I didn't like the look. I used the old speedo enclosure to trace a pattern on some 14 ga. aluminum sheet, and then laid out my new speedo and 4 gauges inside the template. It was pretty crowded to get them all in, and I could even think of adding another gauge or the tach. But it came out good, and fit pretty well. Did have to be very careful routing wiring and pickups on the backside before setting it in place. But that made it easier if I ever need to service it too. I can pull connectors and just pull the whole cluster out if needed. Pre wiring is the way to go on everything you can with the panel.
Post a picture of what you're starting with, and it will help us help you!
I need the whole dash. There is a panel on top that bolts in below the windshield, I have that. A pic wouldn't really show anything, I got to sand blast the panel. I could come down from it with a flat piece of sheet metal and put a 90 on the bottom, but I want to do something to add a little to it. I'm going to fab me a gauge panel. Got all the gauges, except for a speedo, 2 5/8s, got all the led lights for the turn signals, bright light. I'm building my steering column and using the old style turn signal deal that clamps to the column. Been trying to locate a old style custom steering wheel with the 3 spoke and holes in them.
I had a Chevy coupe back in the late 60's, but don't remember the top being separate from the bottom? I do remember the full width center being a separate piece, but the rest of the dash was one piece that dropped down on both ends to below that center. Like this one:
If yours is the same similar dash, then I'd make up a cardboard template, and trace it on an aluminum filler. Then find a person locally who has a bead roller and can roll some pattern into the gauge area to border your gauges. And maybe also roll some vertical or horizontal patterns into any open areas.