I would experiment with old transformers if I had them on hand, or they were inexpensive to aquire in some instance. But I cannot think that really old iron will outperform purpose made MC stepups of modern manufacture of quality, if the prices are comparable. I suppose that someone got ahold of some old iron cheap and made successful cool looking setups for MC stepups, but maybe they are not worth paying a premium for unless you are a cultist or want bragging rights or someething, like look, my xfmrs are real WE, not Lundahls. And old xfmrs were not necessarily designed for wide frequency responses either. But if I had some xfmr pulls from old eqt. or NOS that I thought would work, might go ahead and try it on the cheap.