My mongoose was 130, so I built a new rear wheel with 26" hoops laced to a shimano 105 8 speed hub I got a good deal on. Don't know why that wouldn't work for you. Of course that added another $100 or so to the conversion costs, especially after considering new cassette/chain.
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Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"