GAUGE INSTALL ?

OK, I'm installing some aftermarket mechanical oil and temp gauges. and I am trying to find a good place to drill the hole for the lines to go through the firewall. and 65 darts don't really have many places to drill through the firewall because they are so narrow. if anyone can give me an idea of a good place to drill it would be very helpful. thank you,
As Dana said, use the hole for the speedo cable. I acquired another grommet for that hole, and it allows for a braided oil pressure line and a 1/8" line for a vacuum gauge.