It depends. For some people, a lot of the fun is customizing it. But even if someone built their own from the ground up, it would be from a set of known parts.

[ This is where a parts catalog would come in handy but like hell does a city this advanced print paper catalogs. ]

I could really use a screen in here to cast references to...

[ In the meantime, what he can do is show it to Dettlaff on his phone, swiping left and right shows the same kind of part for different models. ]

Sometimes all that's different is the size or the style, sometimes it might be for different performance priorities.