One of these?
In theory, you could spread the rear end (as it's steel) to accommodate the wider hub you'd need and use a chain tug with derailleur hanger.
But you'll have no cable stops and might run into clearance problems between the cassette or freewheel and the chainstay.
Much less painful to sell it and buy a frame designed for what you want.
@Scilly.Suffolk started
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One of these?
In theory, you could spread the rear end (as it's steel) to accommodate the wider hub you'd need and use a chain tug with derailleur hanger.
But you'll have no cable stops and might run into clearance problems between the cassette or freewheel and the chainstay.
Much less painful to sell it and buy a frame designed for what you want.