Because the builds can be for a specific customer’s needs, there are some quite odd pieces out there, like a single chassis holding a phono stage and crossover. This reminds me of an establishment in the M.A.S.H. novel: Finest Kind Pediatric Hospital and Whorehouse.
I have a custom built linestage by their Italian builder that has a transformer output that is intended to match with the transformer inputs on my amp which is a copy of a Western Electric 133 amp; my amp has original Western Electric input and output transformers. Many of the other parts are vintage as well. The big challenge with this sort of build is finding matching parts, particularly because the only way to know that a part is good is to try it in-circuit.