Can i run an EVGA GTX 260 Video Card with a EVGA GTX 275?

Hi i was just wondering if i could run a VGA GTX 260 Video Card with a EVGA GTX 275 with a SLI Ready system.|||You can run both cards but you cannot SLI them. That's one of nVidia's shortcomings. ATi's CrossfireX can do a 4870 and 4890 but SLI has to have identical cards.