  For a vertex operator algebra $V$, we construct an explicit isomorphism
between the space of genus-0 conformal blocks associated to permutation-twisted
$V^{\otimes n}$-modules and the space of conformal blocks associated to
untwisted $V$-modules and a branched covering C of the Riemann sphere. As a
consequence, when V is CFT-type, rational, and C2 cofinite, the fusion rules
for permutation-twisted modules are determined. We also relate the sewing and
factorization of permutation-twisted $V^{\otimes n}$-conformal blocks and
untwisted $V$-conformal blocks. Various applications are discussed.
