I remember that car. Obviously, you "got a guy". I would use a smaller diamond on the dash. 1" maybe... You also need to use a Sun "Monster" tach mounted large and proud. Or the Autometer version. Don't use any modern exposed wire loom on the wires. Friction tape would be my choice.

Or, again thinking '70's, a zolotone finish on the dash might look good. Powdercoating wasn't something available to the home builder in the '70's. It was more what was available at the local auto parts store, speed shop (remember those?) or hardware store. We learned about trends from monthly magazines that were already 3 months behind the trends.

Olli