That can be done in work O(2^80) (and massive storage), or various time memory tradeoffs with lower storage and more work.
While work might become feasible, a successful attack on P2SH needs more than a collision: an alternate script valid and redeemable by the attacker.
The attacker uses a 1-of-N multisig redeemScript where the first public key is legitimately his and the other keys (up to 130 bytes) are what he keeps twiddling until he finds a collision.