I dont like the idea of coldsetting old frames so here is a perhaps crazy way out of the dilemma of beautiful old steel frames:Why cant someone make a freewheel whith 5 cogs but modern spacing and ramps and all the whatnots of modernday shifting tecnology ? I have an old Gianni Motta Personal, the earliest in the Bulgier files, but I dont think I will ever use it because I have become addicted to brifters.
I will not make it into a singlespeed or fixed, it is a racing machine not a toy.

Souds like a number of personal problems. If a real demand were there,someone would do it. FWIW, there are 5 speed index capable freewhels that are shimano index compatible.Duno what spacing they require.