I think you meant "PK", not clustered index which can, of course, be different.
Absolutely understood on the concerns over SELECT/INTO. I've build some huge tables with it over many minutes. So long as it's on the same server, I've not run into any problems even on busy servers. I definitely wouldn't use it across linked servers because it will sometimes "freeze" the source DB (and it was truly embarassing when that happened to me).
--Jeff Moden
Change is inevitable... Change for the better is not.