I just built up 3 older retro steel bikes,i found most new parts that are available fitted,except for my 126 mm rear spaced hub which i salvaged from an old bike,some places and online stores do some remakes of older parts but they are very few,I just used all new components that were available everywhere,custom built my own wheels,changed out that old bottom bracket for a nice new sealed one,when i was short of a little part i went dumpster diving,thats a very good parts shop,if the part does not show up in google anywhere than you most likely cant get that part,if you want to build up an older bike with all original components than that road is going to take a very long time,most new components will still fit just about any older bike,thats the road i went down a total re-build on 3 bikes with all modern light alloy components,even doing it this way is quiet time consuming,and its only worth it really if you do all the work yourself,some people sell new old stock parts on the net but you dont get A1 gear,its a hit and miss and not really worth chasing them up,jump in and start building,have fun doing it cheers.