I have never tried this, but one might be able to cross-thread retap the right side for a right-hand thread. A friend of mine did something similar with ALUMINUM cranks when he built a tandem and needed two drive-side cranks with left-hand threads and one "left" crank with a right-hand thread, and it worked like a champ, but I don't know how well the technique would work with a steel BB shell.
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"Far and away the best prize that life offers is the chance to work hard at work worth doing." --Theodore Roosevelt
Capo: 1959 Modell Campagnolo, S/N 40324; 1960 Sieger (2), S/N 42624, 42597
Carlton: 1962 Franco Suisse, S/N K7911
Peugeot: 1970 UO-8, S/N 0010468
Bianchi: 1982 Campione d'Italia, S/N 1.M9914
Schwinn: 1988 Project KOM-10, S/N F804069