I think Alfred Werner is currently upgrading Ecommerce to work with openacs5.x. Beta testing should be soon, and your participation would be appreciated I'm sure.
If your need is immediate, and you decide to use 4.6.3, you might save some time using this version as it includes some of the bug fixes reported in the bug tracker, and does not yet include some of the adaptions to 5.0 that are in CVS (that break ecommerce running with 4.6.3.)
There's also ezic-gateway there, an alternative to authorize-gateway (and templated from it) which does not require dqd_utils. It's still in beta, as it has not yet been verified to complete refunds made through the interface.