A great question.
First lets discuss how boats get built. Old - boats are referred to as being feminine - Mature boats were designed and built starting with the Hull. Some interiors were then built into the hull. As the industry developed some designers modified the interior build using a prebuilt pan that was inserted into the hull. This gave the builder the bones to then start adding the "parts" you asked about. Not being Ford or GM, the builders searched about for parts from various manufactures, many still in existence, who provided the quality and price point they desired. Parts were added to the interior to provide the luxuries of living on a boat: Toilets, Stoves, cushions, beds, hot / cold water etc. The deck was laid on top of the hull and the same approach was used to add the mast and all the rigging.
If one of the winches breaks or a block explodes, there are 5 or 6 manufacturers building modern blocks to be used to replace the one that has failed. The new equipment maybe named Harken or Lewmar and not Barient (as was popular in the 60's-70's) but it will be functional and often be greatly improved over the OEM product. You will also find new gear that does a better job at sailing the boat.
Parts choices are about function not original equipment.
There are still some European boat designs that use high end special parts, but in the boat market you are exploring, there should be no problem finding something to work and keep you sailing.