Does anyone have or know where to get a chart of materials to build a harness for a '34 Master coupe? I have enough old harnesses to copy from, but a list of gauges and lenghts of material required would be a great help.

All right,

Here's the same question worded differently: Are all the wires in the harness of the same gauge? If so, what is it 16? 14? 12? I'll figure out the lenghts with a tape.

I don't expect any of us would know the wire gauge of each wire. Also most don't know how to tell if a given wire is a 14 ga. or 16 ga. If you have an old harness I would suggest you measure the wires and then run them from terminal to terminal and after they are all run then tape them into a harness. At least that is what I might do.

Another way is to use 10-12 ga. on the wires from generator to starter and to the ammeter. 14 ga. in circuits with several bulbs particularly those with either large bulbs or multiple bulbs. If only a few small bulbs then 16 ga. should be okay.

Typical Low Voltage Wire Sizes
Air Conditioning- 10 GAUGE Heater Switch- 10 GAUGE
Alternator- 10 GAUGE Horn Button- 13 GAUGE
Ammeter- 10 GAUGE Horn To Relay- 10 GAUGE
Cigarette Lighter- 14 GAUGE Ignition Switch – 12 GAUGE
Clock- 18 GAUGE Low-Amps Circuits- 18 GAUGE
Coil Wire- 16 GAUGE Parking Lights- 16 GAUGE
Dome Lights- 16 GAUGE Radio To Fuse Blocks- 14 GAUGE
Driving Lights- 14 GAUGE Single Bulbs- 18 GAUGE
Gauges- 14 GAUGE Starter To Relay- 16 GAUGE
Generator (Charging)- 10 GAUGE Stoplights- 16 GAUGE
Generator To Starter- 16 GAUGE Tail Lights- 16 GAUGE
Headlight Circuit- 14 GAUGE Turn Signals- 16 GAUGE
Headlight Switch To Fuse Block- 12 GAUGE CD To Fuse Block- 14 GAUGE
Heater Leads- 16 GAUGE Windshield Wiper & Washer- 14 GAUGE

Wow! Now that's exactly what I wanted. You're in my prayers man.

Go by JunkYardDog's suggestion, but if in doubt use the heavier wire.
It wont do any harm if you use a heavier than required wire for any item but using a wire not heavy enough will cause major problems.
Tony