I'm thinking there is something out there like one or two of these Triumph TR4 column wiring clips that would be neat (#15). It would have a nice factory looking appearance. I can't find a Triumph one for sale, it says not available. The oil cloth is perfect for vintage automotive wiring looms. I use to buy it at work for the phone company trucks. You have a choice of the asphalt cloth or the split plastic looms when protecting wires. There are places on a truck where the plastic loom melts so we used the asphalt loom The asphalt looms comes in all different sizes from tiny to large enough to go over battery cables. We bought ours from Standard Products, in 50' rolls. Its available in shorter lengths online. If your going to make up your own looms use this stuff to make them look vintage.
Also looks at all the products in this catalog, switches, wiring, connectors....... There are all kinds of electrical goodies that come in handy when building cars. One thing to consider is using trailer wiring harness cable from the dash to the rear lights. The cable contains all the wires needed to wire up your rear lights on a car. The wires are color coded to match the standard colors used to wire automotive rear lights on trailers and automobiles and they are already protected in a compact conduit. Makes a nice clean harness. If you use the the correct colored wires you never have to guess which wires are turn signals, brake lights and taillights. I run the loom to a wire connection block bolted in the trunk. Then I run wires from the block to the lights. That way if I ever have a problem I can test the wires for power right at the block without tearing into the wiring. The seven-wire cable works great. You can use the extra wire for an electric fuel pump. It would be better if you can find it in 14 gauge rather than the 16 gauge that is commonly sold. Especially for using a electric fuel pump which draws mare amperage than rear light bulbs do. Also 6 volts systems can use twice the amperage as 12 volts so they require larger wires. Its a really clean installation.
Amazon even has the Asphalt loom for sale (below). Take a look at this Standard Motors Illustrated Parts Catalog, bottom of page C9. This is where companies are buying this loom in bulk and then packaging it in shorter lengths. They have 3/16" to 1" loom. Its neat stuff! I have all the old parts catalogs from work and this catalog I use the most for building hot rods. If you can find somebody to ship you this catalog get it. A parts store might even be able to give you one.
http://www.pageturnpro.com/Four-Seas...lt.html#page/1
https://www.amazon.com/Pico-8213PT-F.../dp/B0002ZGCFK