Electrical metallic tubing (EMT) is a great choice for electrical work because it’s strong and cheap. Check out how easy EMT conduit is to use and see how to install surface-mounted wiring and conduit.
An oldie but a goodie, keep it simple, stupid. Sometimes overthinking something does more harm than good, so remember to keep it simple to save yourself some stress.
Someone who knows their way around a car is certainly familiar with SAE or Society of Automotive Engineers. SAE tools are the ones that are measured in fractions of inches. SAE will also be found on oil and horsepower ratings.